You're in the right place! Your question isn't a trick question per se, but it is difficult to provide a straightforward answer. Mostly that's because the concept of school as a series of distinct phases (i.e. 8 years of primary + 4 years of secondary + 4 years of tertiary) for virtually all young people is a relatively modern thing. As in 1950's modern. Before that, young people would leave school (or continue on) as life called for it. If a young white man's future plans included becoming a doctor, he'd keep on. Young women from a family with few resources would likely leave as soon as they were needed elsewhere.

For most of the colonial era, most young American men (because formal education was not commonly accessible to white women and off-limits for indigenous or enslaved children with a few exceptions) of means would attend university with little formal secondary education, typically just enough to pass the entrance exams. Keep in mind that the average age of a Harvard student in 1810 was approximately 15 1/2 - the students were closer in age to today's high schoolers than today's university students. College was about studying the classics, making connections, and preparing for a career (typically in politics, the seminary, or law.)

That said, there is one thing that would make it impossible for a modern day, straight-A student from passing themselves off as a university graduate for most of American history: Greek and Latin. For most of Western education history, the hallmark about an educated man was the ability to read and write Latin and/or Greek. So it doesn't matter how good at math or or science our modern student is, if they can't translate Caesar's Commentaries of the Gallic War into English, they fail to meet the basic bar for what constituted a university education for most of the 1800's and can't be considered an equivalent.

To agree with /u/UrAccountabilibuddy, among the biggest hurdles you'd run into making this comparison would be language capabilities and I would also add the theological component of study. The other issue is specialization. So, American high school students today are, broadly speaking, being given a liberal arts education in preparation for a liberal arts degree, by which I mean that you're expected to study and have requirements in a broad variety of subjects, as you say "science, math, and social science" (as well as literature, history, the arts, foreign languages, etc.)

That American norm is not widely held either historically or even internationally. So in the UK today for instance, students entering their final two years of high school specialize in particular subject and take their A levels based on that subject. They then generally do their university degree only in that subject. So generally speaking there is simply no normal amount of, say, Spanish that a high school student could learn in class in the United States that a UK student with a Spanish degree will have completed by the time they graduate.

Historically, this is the case as well. So, it's somewhat dubious whether the Islamic medieval madrassas can or should count as a university, but among their standards was sheer memorization of thousands of hadiths, reports of the sayings of the prophet Muhammad and the chains of transmission of those reports and doing all of this in Arabic. You won't find that on any standard high school curriculum, usually not even in the Islamic world. The same goes for Western historical degrees on topics like theology. An graduate from Oxford in theology in the 16th century will simply not have a comparable skill set to any contemporary 21st high school student.