American HS teacher (World History, AP World History, Psychology, and Sociology) here. There are several factors to your question which I will try to address:

1. When I was at University I was studying Classical Greek language as my degree. I loved all the works of Homer and Herodotus and wanted to spend my career learning from Greek texts and teaching others to love Classical Greek at the university level. One day, after class, a professor I was close to asked me to meet with him and wanted to know what my plans were for grad school. Along the way he asked me what I thought my life would be like as a university professor. We talked about it and he asked me if there were any other careers that had ever interested me and before I could answer followed up with: “Because it you have, do that instead.” He wasn’t trying to kill my dreams but life is VERY hard for a professor. The days of professors getting tenure (especially in the liberal arts) is gone unless you are an absolute rockstar. That’s where the phrase “Write or Die” comes from in the world of collegiate academia. There are WAY more people graduating with Ph.Ds in History than there are jobs at universities. This means that you will likely have to have both an awesome dissertation and then follow it up with other important publications to have any kind of job security. Otherwise what happens is you will maybe get hired as an adjunct professor, meaning you will be hired on a 2-3 year contract (maybe full-time, maybe part time) and then will most likely have to start the process all over again.
2. So what happens if you want to try? Maybe you are the person who is dedicated and passionate enough to make it work. Good for you! When you go to a university get in good with your professors, offer to help them with research, do well in your classes, join any groups or events sponsored by the History dept., and try and develop relationships that can guide you and help you find the path to grad school. But I would also recommend you consider getting a second major. I would recommend in secondary education (preferably one that ends in getting your certification). That gives you a back up in case one year you can’t find an adjunct job. It also gives you an out if the path ahead becomes less appealing.
3. What about your degree though? Is it worthless outside of teaching? Yes. Sorry but that’s just reality. The good news is that there are many careers that don’t require degrees in a particular field. Someone mentioned government work and that is absolutely true. My wife had a History degree and ended up doing work for the US Justice Dept before going to law school. The real trick is to make the decision about what you want to do before you go to grad school. Its expensive and a Ph.D in History will not help if you go outside the world of education. If you decide you still want to be a teacher though you could always do a masters in history. That would allow you to teach HS dual credit and/or teach part time at a local community college (full time will still usually require a Ph.D).

If I missed anything or you have any other questions please let me know and I will try to help.

Edits for clarity and elaboration.

Edit for the Mods: I haven’t ever posted here but I saw another response was removed for being anecdotal. If necessary I would be happy to PM with the mod team to prove my identity.

1/2 It is not easy to find a career in history, but neither is it impossible. It depends on what you want to do. For reference, I have a BA in Canadian history and make a living adapting scholarship (usually historical, though not always) into graphic novels. I don't know anyone else who makes a living this way.

Anyway, there are a few things that you can do with a history degree.

1. Almost everyone I know in a history PhD program under 40 is struggling (and that's a lot of people, because of my line of work). The post-secondary (college and university) job market is crowded relative to the number of qualified applicants. Universities are in the middle of a process of getting rid of full time faculty and replacing them with contract instructors who work the same hours for less pay and benefits. Tenured faculty and these contract instructors are seldom in the same union, which means that there's a privileged class of mostly older professors who aren't necessarily very invested in the wellbeing of their younger colleagues.

So long story short it is a bad time to aspire to be a history professor. It's not impossible, by any means, so I'll return to that below.

One notable career I want to spotlight in history is teaching in high school. You're in high school now, I'm assuming based on your age, so maybe it's a high school history teacher that has helped you fall in love with history? A public school teacher generally makes more money than a contract instructor but less money than contract faculty. It also varies dramatically by jurisdiction. Where I live, high school teachers start off making between $40,000-$60,000 CAD a year. They can end up making $100,000 CAD a year. It's a 9-5 job though they have to take their work home often as not, and they get two (unpaid) months off every summer as well as march break and Christmas. All in all, where I live it's a solid middle class job. This has a lot to do with the power of the teacher's unions, one of the most successful public sector unions.

In other places this is not the case. There's been a wave of union militancy in the teaching profession in the United States in part because things are so bad. The good news is that these strikes (and fear of more strikes) may improve wages and working conditions for teachers in America. If you are thinking of teaching high school history I would recommend looking at the job market in different jurisdictions in your country and move somewhere that there's a demand for teachers and fair compensation. Moving all over the place is something you'll likely have to do if you want to teach university-level history, I know people suffering in Grand Forks North Dakota because it was the only place they could find two teaching positions (one for each of them).

Anywhere they pay teachers well it's likely a competitive field so expect to spend a year or three on the supply teacher list while you work to secure full time employment. Not fun, but neither is an apprenticeship in the trades, usually.

There are a lot of other jobs in history apart from teaching, though! Archives is an adjacent field to history, and you could do an MA in archival science after a BA in history. Archives make history happen in a very real way and they are a cool place to work - my mom worked at one her whole career. Governments also do have some history jobs. Someone has to write those historic plaques you see on the roadside. Then there are historic sites where there are jobs as an interpreter (pretending to be a historical person) or eventually in developing content for the sites. I had a friend whose sole marketable skill was playing the bagpipes but it got him a job at a historic fort, which later got him into lots of other museum jobs. And yes, apart from historic sites there are historical museums. There's not a lot of these jobs and they have limited prospects for advancement, but they are very definitely a way to work in history.

I have done some work as a freelance historical researcher and that's a career unto itself. All I will say about it is that it is almost never a 'first' career. You may get your first research gig as an assistant to a professor, or you may work in government and make contacts with people there who can hire you as a freelance researcher. Either way freelancing is long hours and precarious employment, but it can be both fun and liberating if you're hungry enough to make it work.

If you're daring you might try your hand at writing popular history but you should have a day job too. Similarly, getting hired as a historical consultant in TV or video games can be an ok gig but is no way to make a reliable living. There are also history magazines where you don't need to have a PhD to be published, but again, that's gig work and not a career unto itself.

Oh I've almost forgotten one of the most reliable ways to do contract research: genealogy. If you don't mind spending your days digging through immigration records and family trees, people will pay you to tell them what year great-granny came over on a coal steamer from Liverpool. Though these days it might be great-great granny. You might be able to make a decent living as a contract researcher and genealogist especially if you park yourself somewhere close to major archives (in the US I would say Philedelphia is a solid choice because you can easily take the train to either NYC or DC, sites of major American archives, not to mention there's plenty of interesting archival stuff in Philly too.)

There was a time corporations would keep a historian or two on staff but that has, alas, become quite unusual.

So all in all I hope you can see that a history degree isn't a reliable pathway to riches but it is absolutely a viable career choice and there are a ton of things you can do with it other than teach.

2. In spite of the recent credential inflation (a Bachelor of Arts is worth less on the job market than it used to be) there are still many job postings that list a university education as one of their prerequisites. So counter to what people may tell you, it is possible to get an education in history and find work in all kinds of fields. Typically this means working for non-governmental organizations, unions, potentially historical societies if you're lucky. But these aren't history jobs, I'm just mentioning them to emphasize that a degree in history is not the career suicide it appears to be.

3. If you want a career as a professor, or any career in history, the advice is the same: study hard! But also learn the meta of university. When your history department has guest speakers, be there. Ask one smart question per three events. If the history department has a pub night where you can meet profs, go to that. Network, network, network. Not everyone will tell you this but academia is all about who you know. You will need 3 letters of reference from professors who taught you if you want to go to grad school. So make sure you have three professors that genuinely love you and want you to succeed.

When you're writing papers, figure out who's a working expert in that field and write to them asking for recommendations. I did this as an undergrad and you wouldn't believe how often scholars with PhDs and tenure took time to write back with useful information that made the essay writing process WAY easier. Speaking of writing, if you're serious about grad school, you should try to get published (even if it's just as a co-author) as soon as possible. There's a reason they say 'publish or perish'.

Start learning about how academic grants work where you live. Volunteer to proofread grant applications for grad students. There is a whole hidden machinery to how academic life works and no one is going to explain it to you unless you get lucky and make a good impression on someone helpful. If there are student seats on your university senate (if it has a senate) try to get on there! You'll learn a lot about the way institutional politics work. In all of these things listen, learn, and guard your real opinions. Academic life is very political and it's easier to make enemies than you might think. Everyone likes a student who is helpful, respectful, a good listener and volunteers for things.

Firstly, you may have people try and push you into a career in law or tell you that a career in history is unreasonable; but if you are passionate about it, don't listen to them.

To answer your questions:

1. The education field. To be upfront, I am not in the education field but I do work with a good number of history teachers in my job. Biggest pros: there are jobs available, it is a surefire way to teach history, and it is a somewhat stable paycheck. Cons: you may not be able to start teaching history right away, there is a high turnover in education, teaching is very stressful.
2. If you look towards museum education, your training as a teacher will be seen as a benefit. Many people forget that there are ways to teach history outside of a traditional school setting. Now for most of these jobs, you need graduate education but there are a host of options with one of the best being pursuing a master's in Public History. One thing you can do is, when looking at colleges, see if the school has a history for teachers track. My undergraduate did and it basically meant that the students were getting a double major in education and history. In a sense the best of both worlds for what you are looking at.
3. Right now, I would suggest focusing on finishing up high school. You don't need to have your life fully planned out before you go to college but if this is something you really want to pursue, incorporate this into your college search. Look for schools that have strong history/education programs. Don't just look at the big schools, look at small liberal arts colleges as well. When you get to college, start looking for internships. These will help you narrow down what you want to do as a career.

I hope that this was helpful.

Source: I currently work in museum education at a history museum and wanted to teach history when I was 17 as well.