1) i would not do weight at such a young(??spelling??) age
due to the fact that he is still growing and the weight lifting could effect this.
(dunno how this is called in english) but when he has to strong muscles the bones cant grow right or something and he might end up with some back problems or thing like that....ehrg some 1 els might explain this in a better way..
2) running, skipping, sit up's, and thing he should not do at his 12th year
(involves a female)
3).......