As a plus, school may introduce people to topics that may interest them and then allow them to find their way in life: from playing an instrument, to gymnastics, to computer programming.
Grades are a fixation of the school system and of all those involved, but they don't measure knowledge accurately. Some companies may not hire you if you have low marks or studied in a less than prestigious school/university, but that has not necessarily anything to do with knowledge and is likely to have something to do with class segregation. So there's a point in making them up.
Vandalism being tolerated is instead a very serious issue the school should address.