Working Out-- For a 13 year old?

Ite, im 13 years old, male and i've been wanting to start working out a bit, ive read up a bit and ive herd weights stop growth, so i dont do weights i didnt have any intention at my age to do so anyway. However i have been doing atleast 200 press/push ups whatever u call them and 200 crunches daily, and i just wanted to know does this actually have any effect?, also if it does how long do i have to continue this until i SEE the effects? i was just wondering becuase i have been doing it for 2 weeks and im anxious to find out if my upper body strength will grow stronger or after a while getting some abs/packs thx.