Wtf is wrong with me playing with kindergarten, 1st and 2nd grade boys?

There is a boy who is in 6th or 7th grade and he also plays with kindergarteners mostly and 1st graders too. The only thing is that he is a dwarf, he is only 4'4 so he looks more like a 6 or 7 yr old than a 11 or 12 yr old, but he is also entering adolescence. I am 16 yr old and in 11th grade but i am tall 5'7(171.5 or 172 cm) so i look like a perfect teen. But i still play with paper planes with a kindergarten boy. Even he can play with kids so why cant i....