Kids struggle at times - with themselves, with school, with life.
They become misfits within the system. Temporary misfits.
In 99% of all cases, this struggle has one of two causes (or both):
1.) It is a personal crisis.
Separations and divorces, family troubles and illness can deeply unsettle a child.
The chief troublemaker however is and always was puberty.
2.) Place and company aren't right.
The school isn't compatible with the kid's personality, the curriculum doesn't match its talents.
Wrong environment, wrong direction, if you like. So, it is hard to see the point and the goal.
In addition, mobbing can ruin all remaining motivation.
No child, no teenager, is ever "a problem to be solved".
So, you're a teenager. In school, you're not doing well at all.