Cause it feels good
A dog's love is unconditional, safe, fuzzy, warm, reassuring that you are loved.
Playing or interacting or eating with others at school can be scary, one can be made fun of for almost anything that doesn't fit their concept of 'fitting in'. Take some chances, mstart with someone it feels safe with. Each experience that is positive, reinforces and gives you incentive for the next. Courage, boy.