My first thought upon reading your question was for the Edinburgh Royal High School riot in 1595, which really was in response to the students' perception of administrative abuses. The story is as follows:

In the autumn term of the royal high school in Edinburgh, the headmaster, one Hercules Rollock, had been harried to maintain discipline within the school. Faced with a particularly wild set of pupils who had an unfortunate propensity to cut lessons and carouse around the town, he was not sympathetic when the students presented their traditional request for annual holiday (the custom of seeking 'the priviledge' as it was known) and instead refused the request and thus cancelling a week of holiday that was, as far as the students were concerned, a right immemorial.

In response, these students who as 'gentlemen's bairnis' considered themselves to be too good for such treatment, 'tuik the scooll, and provydit thauaeselfis with meit, drink, and hagbutis, pistolit and sword', effectively barricading themselves within the school. When Rollock returned the next morning and found his entrance barred, he at first attempted to negotiate a peaceful reconciliation but when this failed, he called in the municipal authorities whereupon John Macmorran, one of the city's magistrates, arrived at the head of a party of men with the intent of forcing the door.

Riled further by the presence of the magistrate and his men, the students warned their besiegers to approach at their peril. As people in such a group dynamic as this are wont to do, the 'defenders' within the school were perceived as both highly excitable and outrageous in their attempts to outdo one another with their threats. Chief among these riotous youths was William Sinclair, 'sone to William Sinklar chansler of Catnes' who, upon seeing Macmorran approach, 'wowit to God, he sould schute ane pair of bullettis throw his heid'.

Dismissing the threat as empty and the students within the school as mere children, Macmorran was undeterred and he and his men set upon the door with a wooden beam that had been turned into a makeshift battering ram. Moments later, he was dead as '[t]hair came ane scoller callit William Sinklar, and with ane pistollet schot out at ane window, and schott the said Baillie throw the heid, sua that he diet presentlie.'

The school was eventually breached, however, and eight students (Sinclair, George Murray, son to Murray of Spainziedaill, Robert Hoppringle, son to the gudeman of Quhytebank, Andro Douglas, son to George Douglas, associated to the Laird of Cesfurde, Raguel Bennett, son to the ‘umquhile’ (former) Mungo Bennett in Chasteris, Adair, son to Adair of Kinhilt, Kirktoun, son to Kirktoun of the Tour, and Malcolme Cokburne) were imprisoned within the Edinburgh Tollbooth (what they called the gaol...not an actual booth for the collection of tolls) while a deputation was sent to King James VI at Falkland Palace to advise him of these extraordinary proceedings. It took two months for the privy council to hear the case (during which time the rioters remained imprisoned in discomfort) but once they came before the king, they successfully argued for the creation of a special assize to try them since not only did they refuse to recognize Edinburgh's jurisdiction over them given that many of them were the sons of barons and lairds from all over Scotland, but also because the city's authorities had been involved as well and could not, therefore, be expected to remain impartial during the trial. The king was persuaded and they were tried...and acquitted of any wrongdoing although the transcripts of the trial itself have not survived to tell us exactly what happened. Just five years after the riot, William Sinclair obtained a remission under the Great Seal for the killing of Baillie John Macmoran. He was later knighted Sir William Sinclair of Mey by James VI.

But Macmorran was not the only victim of this episode as Rollock himself suffered such a great loss of reputation that he was eventually removed from the school and died in poverty and obscurity four years later having unsuccessfully sued the city for maintenance given his former good work.

It's an early modern example outwith America but it's certainly an incredibly interesting historical episode, I think!

Further reading can be found in William Steven, The History of the High School of Edinburgh (Edinburgh, 1849).

There was a series of high school walk-outs and strikes in the late 60s/early 70s, yes. Leaving aside those that were racially motivated, these demonstrations tended to be motivated by conflict over things like dress codes (especially: young men's ability to wear long hair and grow beards, or young women's ability to wear pants or mini-skirts), a popular teacher being fired, or schools not permitting students to protest the Vietnam War. Other issues that might provoke a student strike or demonstration were censorship of school newspapers or the banning of "underground" high school newspapers, students' ability to smoke on school grounds, students being disciplined for using foul language, etc.

Basically, school administrators and teachers had run a very tight ship up to the mid- to late-1960s; student behavior was closely monitored and controlled, and you could get in trouble for a lot of things that students today do all the time; wearing unconventional (by the standards of the time) clothes, making controversial political statements, smoking, having the wrong hairstyle, etc. But during the 60s, protests by college and university students like the Berkeley Free Speech Movement, Vietnam War protests, and the spread of 1960s counterculture spawned a wave of similar protests in schools, which directly challenged administrators' and teachers' power over students.

To my knowledge, none of these kinds of demonstrations or disruptions were severe enough to be called a "riot" - most of them were pretty tame by our standards, though they were often considered serious disruptions and challenges to school authority at the time. But if we include the racially motivated protests and demonstrations (and there were a lot of these) then yes, some of these did become very tense, involving destruction of school property and occasionally violence. Remember that this is a period when schools in a lot of different parts of the US were finally being integrated. Despite the fact that the Brown v Board of Education decision had been handed down more than 20 years earlier, a lot of school districts had taken every opportunity to drag their heels on actually carrying out integration in practice - so it wasn't until the late 60s and early 70s that the courts started handing out injunctions and ordering measure like bussing to actually integrate the schools.

As a result, there was a lot of racial tension within many schools when black and white students started sharing classrooms and other school spaces for the first time. Black students frequently protested and demonstrated against what they viewed as racial discrimination in the school. Of the examples that I have read about, they often tended to be most upset over a lack of black teachers, a biased curriculum that taught very little black history (and may even have been overtly racist), harassment and discrimination by white students, unequal representation of black students on school sports teams, cheerleading squads, etc, or even segregated prom "courts" where you had a "black" king/queen and a "white" one.

There's a decent book about this stuff if you're interested, Gael Graham's Young Activists. You can also check out her article in the Journal of American History from a few years ago called "Flaunting the Freak Flag" (the title is a reference to boys wearing long ("beatles-style") hair, which believe it or not they had numerous lengthy court battles about during this period).