When should you wear a padded bra?

There's no age when you 'should' wear a padded bra, if and when you wear a padded bra is up to you. Unless you have large breasts that need the support there's really little need for someone to wear a bra at all, especially if you have smaller breasts.

Some girls prefer padded Bras as they feel more covered or it can help hide budding and uneven breast size during development. If you feel like you'd be more comfortable in a padded bra then get one, there is no restriction on when you can or can't wear one.