All shows set around school and teenagers should end after 2-3 years. It never works with them growing up
They set up those high school teen dramas when characters are around 16 years old. Then pretend they are in school for next 4 years. Then have to acknowledge they have to graduate and send them to college. And all the school charm is lost and viewers lose interest.
Show still try to milk that cow go on for few years despite sinking ratings, then eventually give up and cancel.
90210, Glee, OC, Buffy, Dawson Creek, Gossip Girl and so on. Basically every show set in school. They really should not be greedy and have and end date for those shows by doing only 3 seasons then leaving those characters alone and go on top. Not being cancelled because no one watches it anymore.