Followup question: When did these novels become standard parts of the curriculum? And what did American students read before these novels?

Despite the efforts of some of the founders, most notably Jefferson, education in the United States falls under the 10th Amendment of the Constitution, which means it's up to each state and territory to determine what children do while they're in school. There are some exceptions and parameters, especially with increased federal funding via Johnson's War on Poverty and the elevation of the Department of Education to a cabinet-level agency in 1979, but generally speaking, states determined the look of school. This means it's difficult to speak to an American school history.

However, as your question highlights, there are similarities between schools across the country. Walk into a school in Alaska or Florida and you'll see what you expect to see. These common things - desks and chairs, colorful decorations, separate bathrooms for boys and girls, etc. - are known as the "grammar of school." (Tyack and Cuban, 1995) They are the seen and unseen things that make school recognizable as a place where children learn. Passed from generation to generation primarily via cultural transmission and tradition, they contribute to a shared understanding of what school is supposed to look like. Some of the features of the grammar of school are national (nearly all US schoolchildren refer to their teachers by a gender identifier and the teacher's last name) some are regional (students in the northeast start summer vacation in July, students in the southwest start in June.) Some have clear pedagogical purposes (calculators in math class) while others are because it's "always" been that way (young children walking single file down the hall.)

Where the list of books in your question and the grammar of school intersect is in the traditions of English class. To be sure, no one with any real authority has ever stood up and said: students will read these books for this reason. Books end up in front of students for a variety of reasons after following a variety of paths. More to the point, each of the books you listed is just as likely to have been banned or appear(s/ed) on an informal prohibited books list as having been read by a high schooler somewhere in America. It's helpful to look at feedback loops between HS, society, college, and the canon.

For most of the 17th, 18th, and parts of the 19th century, students in formal education (mostly white, mostly boys, sometimes girls) experienced a classical curriculum: Greek, Latin, some math, some sciences, including logic and rhetoric. The goal wasn't to develop a fluency with Latin in case one ran into a Roman ghost, but to build a young man's thinking skills so that he would be prepared to think deeply about whatever he needed to think deeply about. There was, however, a hierarchy of valued content. Latin was near the the top of that hierarchy, mathematical knowledge was somewhere in the middle, and studying history and literature were near the bottom. Those who shaped what students would do, tutors and school headmasters (virtually all white, virtually all men, mostly located in or from the northeast) typically viewed reading literature as something that was either a waste of time or akin to talking a slow walk while training for a marathon. If a society didn't see something as essential to their children's success as adults, it likely wouldn't appear in school. Ergo, literature was often left out.

As schools became something more and more something children did, not just the sons of white men with means, there was shift from a brain-building (classical) education to a more practical, useful (modern) curriculum: math, science, history, modern languages, English, Greek/Latin, music, art, physical education, etc. This shift included a bit of a shake-down of the hierarchy, which felt chaotic and inefficient to those in charge of formal education at the local level. Those men, known as "schoolmen", felt this problem, like most, could be solved by a committee.

In 1893, The National Education Association pulled together a series of committees of school leaders (all white, all men - even those from girls schools or women colleges) from across the country, to describe what was happening in schools and make recommendations for the look of high school in the new century. They had no national authority and were more describing what was popular at the time, than necessarily what could be in the future. The English committee made it clear they wanted the study of literature "to be made an equal" with studying Greek/Latin even though the idea was new and perhaps uncomfortable to their fellow schoolmen. (As a reminder, literature, especially modern or popular lit, was seen as a waste of time to those committed to a classical education. If you're familiar with the Reading Wars of the mid-1900's, that was a gentle skirmish compared to the modern vs. classics curriculum battles in the late 1800's and early 1900's.) In their report, they laid out a clear and explicit argument for studying literature: "to cultivate a taste for reading" and to give the pupil "some acquaintance with good literature." The men in this sub-committee were there because they had opinions: primers were okay in grammar school but by the 7th year of formal education, English class should focus on prose and narrative poems ("sentimental poetry should be discarded") and whole books. They advocated for 480 total hours reading, discussing, and writing about "good literature." They go on to describe the quantity as:

That the reading of certain masterpieces of English literature, not fewer in number than those at present assigned by the Commission of New England Colleges, should be required.

The nature of "good" is where the canon comes in. The canon is recognized as the books, poems, texts, and plays considered essential to being an educated person. The American canon tilts towards American-born authors and is predominately authored by white men. This lead to another feedback loop: the men on the committees went back to their high schools and told their teachers to teach good literature, teachers pulled from the canon and young people who became teachers used those same books. Whole books became part of the grammar of school in HS English classes.

Another feedback loop emerged around college admissions. Most colleges, especially those with a high degree of prestige, had their own admissions requirements down to which Latin text a student was expected memorize, which was likely to be a different Latin text than the prestigious university the next town over. Eventually, colleges talked to each other, listened to high schools and mostly evened out admissions. However, high schools that wanted to brag about where their students went to school would focus on texts they knew appealed to a particular college admissions' officer. This feedback loop lead to the creation of lists and programs, including Great Books and Junior Great Books as well as the National Conference, a group of university and college representatives who established the list of classics that students would need to know and be able to write about for their entrance exams.

Concurrent to these changes around curriculum, the teaching force itself was changing. For generations, it had been a temporary thing a young woman (mostly white) would do before getting married and having children. Much like the push for voting rights, women challenged the notion a woman couldn't teach and be a mother and that the job of being a teacher required professionalism. However. America being a country with deeply sexist roots, well-meaning schoolmen felt teachers needed guidance and help. This sentiment lead to the creation of professional education organizations, such as the The National Council of Teachers of English. Founded by James Fleming Hosic, it was established as a roundtable working group of English teachers and members of the National Education Association in 1911. Unlike the 1894 Committee of Ten, the working group included practicing teachers, many of whom were women (who wouldn't be trusted with leadership positions for years.)

Increasingly school leaders pushed back against the idea of colleges having say in what students in secondary school did and one of Fleming Hosic's goals was to advocate for high school curriculum written by high school teachers based on their goals for their high schoolers - not college admission criteria. Slowly, high school became less a place to prepare for college and more a place that teenagers went. NCTE held (holds) annual conferences where teachers would model curriculum, share lesson plans, reading lists, and diffuse knowledge about English class across the country. As some districts linked teachers' evaluation to participation at such conferences, attendance was high and lists were widely circulated.

There's one last shift that needs to be addressed before we can get to the particular books on your list and that's the idea that school should be a place that is accessible and welcoming to young people. Progressive education advocates suggested the radical notice adults should consider children's interests when planning curriculum. This notion, spread through conferences like NCTE, meant teachers were increasingly choosing whole class books that reflected current events or ones their students wanted to read. This lead to a shift in what's thought of as canon - all of the texts you listed are now considered part of that canon and have appeared on an NEA or NCTE list or conference session.

The books on your list became part of the canon because teachers felt they'd appeal to a young person sitting in English class as they deal with authority, social stigma, and rebellion. So, one last feedback loop. Young people read those books in school, grew up to become teachers or curriculum directors, and teach what they were taught.

/u/UrAccountabilibuddy gave an excellent overview of general pedagogical trends in high school English education, but I thought I could add some information about why those books in particular are so popular.

First, I want to say that you're right to think that books written in the 50s are particularly common on high school reading lists in the US. It's an informal source, but the Goodreads poll of Required reading in High School reveals that most commonly read books were written in the 20th century, with peak publishing years in the late 40s to early 60s. Here's a breakdown of how many books in the top 50 canon were published each decade:

Decade	Top 50 Books in Canon Published
1900s	0
1910s	2
1920s	2
1930s	3
1940s	5
1950s	7
1960s	4
1970s	0
1980s	0
1990s	0

The canon was largely formed in the 1960s-1980s, and has remained remarkably consistent in the last 30 years, aside from a stronger focus on works of literature by female and minority authors. A report from 1988 that found the most common taught works of literature includes many that would be recognizable to most high school students today, including post-war books like To Kill A Mockingbird, 1984, Lord of The Flies, Diary of a Young Girl, The Crucible, and others. In contrast, a similar study in 1963 found that only one of the top ten most read books was published in the 20th century. Furthermore, the canon stabilized in that same time period- the number of books read by at least 30% of classrooms tripled between 1963 and 1988.

So why were books written in the 1950s so much more likely to have made it into the canon? Partly this has to do with the canon stabilizing in the years after they were written- books that were popular in that time period would have been on the minds of educators, and many of the books in the canon were bestsellers. Partly this has to do with, as /u/UrAccountabilibuddy mentioned, a transition to books that were relevant to the struggles and experiences of adolescents, and a subsequent increase in publishing of said books. According to a 1974 study:

"The forties saw the development of a new literary, genre with its own authors and highly specialized audience of "adolescents" as defined by the "life adjustment" educators"

Books said to be part of that genre include Anne Frank: The Diary of a Young Girl and The Catcher In The Rye, both of which are still popular in high school curricula today. Finally, the cultural ascension of Baby Boomers might have played a role in preserving certain books in the canon out of nostalgia or familiarity, paralleling the domination of Christmas music released in the 1950s on the year-end music charts.

(This is not history, but it may be that we're in a time of another large shift in the US high school English canon, away from 1950s books. The Common Core List of Exemplary Texts doesn't include any of the books you mentioned except for Fahrenheit 451. Instead, it includes a much greater number of works of literature by women and minorities, and a much greater emphasis on non-fiction texts, which it says should make up 70% of a year 12 curriculum. One paper said that these "text exemplars will become a new canon for literacy instruction, a kind of national reading list.” )