What is your standard of fitness?
If you are healthy, working normal can play, run, jog, alert in the class and in the play ground.
Pray 5 times, read Quran-e-Pak to understand to be a good human being and true Muslim.
Get good grades in the class.
Obedient to your parents, teachers and elders, nice to your friends and siblings.
Have good habits and character.
This means you are fit.