Do you mean you want to wear makeup or that you want to be a makeup artist?
Considering your age and circumstances, I'm going to assume you're looking for advice on how to ask for permission.
First of all I think you're old enough to wear makeup, but I get the impression that you have reason to believe your "uncle aunt grandpa and grandma" (I'm going to call them your "parents" ) don't.
Secondly, I think you're better off getting your "parents;" permission to wear makeup than pulling the old trick of putting in on at school and then washing it off before you get home. Assuming you're not talking about wild makeup like the following, I don't think the old trick is a horrible crime and it's been done by thousands upon thousands of girls your age in the past, but you'll run the risk of having your "parents" find out (You never know. Parents are always at schools during the day. A friend of your "parents" might see you and tell them. One of your "parents" might unexpectedly come to your school and see you. As soon as you create a scheme that requires something never happening, you can bet your life it will happen). If they do find out and you didn't ask them for permission, they're probably not going to be very happy that you've been sneaking it. I don't know what sort of punishments they hand out, but if I were them I would tell my daughter that now she was forbidden to wear makeup until she was 15. Beside, it can be stressful running a scheme like that.
Here's what I suggest:
Set your sights low. If they agree to it, it will likely be a modest amount of makeup and nothing wild or too mature.
Give them an indication of what you want to look like so they don't immediately conjure up images of you looking like a hooker or a Goth Queen.
There are two ways you can do this:
The possibly riskier (depending on how strict they are) method is for you to go to one of your friends' houses, apply the modest amount of makeup and take a picture of yourself that you can show your "parents" later.
The second way is to find a picture online that shows a girl wearing a modest amount of makeup and telling your "parents" that you want to look like this girl:
These are just three pictures. You can find lots of others if you do a search on Google Images using words like "modest" "minimal" "teen" "makeup"
Try and find one of a girl who looks similar to you.
The third one above is an actress Chloe Moretz. If you know one who your "parents" really like because they think she is a "nice girl," you might want to go with a picture of her.
Do not use anyone like Miley Cyrus.
Good luck (don't sneak it