There are a BUNCH of super obvious choices for this that I tried to avoid -- much of the John Hughes oeuvre, all those "take a literature classic and set it in high school" movies (sorry, Clueless), and Carrie. I tried instead for some deep cuts, or at least semi-deep or underappreciated.
So here goes. My "five because" high school movies:
#5: Grease 2 (1982)
#4: Splendor in the Grass (1961)
#3: All Cheerleaders Die (2013)
#2: Pretty Maids All in a Row (1971)
#1: Sing (1989)
High school was tough for me, as it was for nearly everyone, but it was made more tolerable by my taking part in artistic pursuits (in my case, marching band, winterguard, and madrigals). This movie is based on a real thing that is still going on in high schools in New York City -- student-run musical productions called "SING!" that typically pit classes against each other in competition -- and since seeing it in my own high school years, it's low-key one of my favorite musicals. The movie takes place at a school in Brooklyn that's facing closure in a community that's crumbling, but they want to put on one more SING! show because it's an important event not just for the school but for the community at large. There's a sweet opposite-sides-of-the-tracks romance, and several genuinely good songs (okay, "Birthday Suit" is hella cheesy, but "Romance" is lovely and all the SING! numbers are great, especially the heart-stirring "One More Time," which feels like a classic David Foster tune, and "We'll Never Say Goodbye," the greatest school song that never was). A lot of the movie is dour because these people's lives are tough, but that only reinforces the joy of the movie's last act, when the community gets together to cheer on the next generation, even against the admonition of the school board. The movie features Lorraine Bracco *just before* she was in Goodfellas, and even Patti Labelle in a minor role, but most of the rest of the cast is made up of lesser-knowns. It's hard to acquire, unfortunately, but the whole thing is on YouTube.