I think it's important to let a person have enough responsibility to decide what they are going to wear. I'd encourage that at a very young age. Teenagers and children are people. The more they are made to be the effect of their environment through controls relating to what they can or can't wear, or can or can't have, the less responsibility they can take for their own actions.
In a society where the right to own property is considered to be a cardinal aspect of a free nation, I think we need to be very careful when we don't allow our children to own and be responsible for property. Once it's theirs, either through a gift, or because they purchased it themselves, I believe they should have the ability to do whatever they choose with it, whether that be to give it away, throw it out, wear it, or otherwise.
It's totally understandable to feel responsible for one's children, but it's better for everyone involved to allow them the freedom to be responsible for themselves, and trust that they will make the right decisions. The right decisions for them may not be the one's you approve of or support, but I think it's still their place to decide. To do otherwise, is to perpetrate a system of bad control, for the purposes of perpetrating it, and to project our mistakes and misdeeds upon them.
I follow a pretty strict philosophical outlook that contends in nearly all situations, children are more rational and more sane than adults. Experience has validated this outlook for me. I think we've often got things backwards.