These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
A highlight of the soundtrack is Led Zeppelin's Immigrant Song. Not just because its an awesome song, but the sheer fact that it's in the movie is a CMOA for the cast and crew, as they were able to convince the band (who is famously stingy about licensing their music) to let them use the song.
Designated Hero: Dewey. Mooches off his Extreme Doormat of a friend, doesn't even try to find work or help with the rent, and takes it extremely personally whenever his behavior is brought up. Looking past the movie's "music is awesome" message, he cheated those kids out of (three weeks of their) education and stole a job from his friend without thinking twice.
After seeing Zack berated by his father in the parking lot, Dewey initiates a class lecture/improvised song about sticking up for yourself. By the end, Zack is feeling much better and even thanks Dewey for the great lesson...in front of the other teachers (who are both awed and slightly jealous).
Even better when you see Zack's father cheering him on during the final performance.
Idiot Plot: Any other adult could have potentially exposed Dewey's masquerade.
Moment Of Awesome: Ned's has to come when he walks out on his crazy-ass girlfriend just as she's shouting at him to try standing up for himself.
Ned's girlfriend Patty, when you really think about it. Dewey has been bumming at their place for months if not years, while continually refusing to get a steady job and therefore doing little to contribute to the rent. Ned keeps doing whatever he can to accommodate him because they were in a band years ago, while Patty is just supposed to tolerate this. It doesn't change the fact that she seems to take joy in Dewey's suffering, but anyone would be frustrated by that point.
The fact of the matter is that most aspiring rock stars, no matter how committed they are to their dreams of music stardom, will not succeed and will have to find some other means of paying the bills. It's not because their drive wasn't strong enough, simply that at some point, Reality Ensues and you have to find a way to provide the basic necessities for yourself.
Of course, the movie sets up something of a False Dichotomy — a lot of people simply parlay their rock star dreams into another career involving music, such as teaching or writing about it. And of course, at the end of the movie, Dewey and Ned do just that by setting up an after-school rock music teaching program. But the way Dewey acted as if it had to be either one or the other doesn't reflect reality.
It's hard to blame Dewey's band for kicking him out — just watch Dewey in action during the opening scene. Being a Large Ham is OK, but he should have known when to tone it down a little. The fact that No Vacancy win the Battle of the Bands without him makes their point just that much stronger.
It doesn't exactly make parents "tightly-wound" for being upset that their kids are learning nothing but rock music, and no academics, for weeks or months on end. Even many rock-loving parents would be bothered by how this would set their kids up for some serious educational problems later in the area (for being behind all the other classes in their grade).
The movie takes place over a total of three weeks (Freddy says "We got a three-week vacation"), and it's implied that all the students are academically successful. It's fair to assume they can catch up with some extra homework. Perhaps it's not the best use of their time or the parents' money, but the events of the film won't kill them academically.