Dd is 12. She has been wearing lightweight crop tops for the last 2 or so years - all good. She is quite petite (/short!) but over the last 2-3 months has noticeably developed a bit and I think she is going to need something with a bit more support than a crop top at some stage. Or do they carry on in crop tops for a while? It was a vest/28AA ladybird bra tradition in my day! So vest clearly became inadequate but not sure re crop tops.
She plays quite a lot of sport so I will get her a thicker/proper sports crop top - that part is quite straightforward I think, as I think the sports outfitters place does those.