Wow I hadn’t thought of that movie in years, a very weird ending. I think it was made to cash in on the success of The Warriors.
The ending was in the book.
It probably had more to do with the success of Animal House (even casting one of the performers). And it wasn’t a lone entry in this competition.
The Baby Boomers were big market and mid-50s-mid-60s nostalgia was in bloom.
Big Wednesday trailer
https://www.youtube.com/watch?v=5hFH3q5bz1Q
Cooley High trailer
https://www.youtube.com/watch?v=zqWDOyESFTY