I think that school memories tend to remain with one while later memories fade. It is such an intense time, growing up with restrictions and among strangers, that the experiences are imprinted on the memory.
I've been finding myself in nostalgic thoughts a lot lately. School had some good times, but mainly awkwardness. There were some decisions I wouldn't mind a redo on.
I agree with you. I had, on the whole, happy and successful schooldays. And yet I remember the things that went wrong, one way or another, much more vividly than most of the the things that went right.