I also watched that in English class. Weirdly enough, my teacher didn't even ask our parents to sign permission slips. Oh well.
My teacher, whose name I've completely forgotten in the time since, was also cool enough to forego the permission slips. She said she thought we were responsible enough to decide for ourselves whether we were mature enough to watch a movie with an
eensy, weensy bit of nudity in it. If we had a problem with it, or we thought our parents would have a problem with it, she gave us permission to excuse ourselves from class and go to the library. As I recall no one took her up on the offer and we all watched it. We watched the Baz Luhrmann adaptation (I call it "Romeo-plus-Juliet" aloud) too, which I didn't really care for except for John Leguizamo, who is great in everything he's in.
The same teacher also had us watch the film adaptation of "To Kill a Mockingbird" after we'd read the book. Before we began reading the book she said "Look, this book has had a controversial history with respect to being read in schools, particularly because it's riddled with a particular racial epithet throughout. The context of the story demands it. I think you're all mature enough to treat this with the respect it deserves." We read the book aloud together as a class, with everyone allowed to volunteer to recite a few pages at a time. Nobody giggled when somebody said "nigger", that's for damned sure, I think precisely because she didn't handle it with kid gloves and treat us like infants.
She adored Gregory Peck, had a
huge crush on him. She cried at the end of the movie, that I remember distinctly. Sadly, as I said, I can't even remember her name. I'm going to have to dig up one of my yearbooks tonight.
EDIT: The next year, Grade 11, my English teacher (whose name I do recall and who was... not my favourite...) made us watch Roman Polanski's
Macbeth. It was considerably more graphic and sensational, in violence and nudity, than Zefirelli's
Romeo & Juliet, and the teacher didn't send permission slips home for that either. More out of laziness than anything, I think. An atrocious movie, that one. I kept thinking to myself, "Ah, so
this is what comes from the mind of a man who thought it was cool to dope a 13-year-old up on 'ludes and sodomize her."
Grade 12 we watched Kenneth Branagh's
Hamlet. We had a substitute teacher that day and she remarked that "Mel Gibson's version was really good!" We laughed because days before our teacher said, "We're going to watch Branagh's adaptation because it's pretty good, and because it was relatively easy to find a copy of it on VHS. Gibson's adaptation is crap."

(That teacher was awesome, he was full of hilarious stories. Like why he was not allowed in Shoppers Drug Marts anymore, and how he bought his wife a toilet for their anniversary.)