I say 14, cause your finishing up middle school and going into high school soon, dnt put too much though, just use eyeliner and maybe mascara :) learn how to put it on right too and than you should be good
remember let children be children. with so many phedofiles out there don't have your children stand out because they are wearing makeup at 7 & 8 years old. they are still babies. once they menstrate is often a good time to allow them to start wearing makeup. Help them to learn to apply makeup at 13 so by the time they are 14 they have it worked out & hopefully don't look like a tart or a clown.
I started to wear makeup at 15, so i would say 15. For most people it isn't even needed very much except for little spots that need to be covered up. My advise for you if you do start wearing it is to be careful how much you actually put on because you dont want to look like a clown.