Whether to wear a bra or not, at any stage of development or at any age, is a personal decision. If you’re starting to develop breasts and you want to wear a bra, you may want to talk to your mom or an older female relative or friend about possibly getting one.
Some girls like to get training bras as soon as they start developing breasts so they can get used to what it feels like to wear a bra. A training bra can also help cover up your nipples, which may stick out and become more noticeable as your breasts begin to grow.
Depending on how big your breasts are, you might want to get a sports bra too, for gym class and any team sport (except swimming).
Just like breasts, bras come in all different shapes and sizes, and different bras can make your breasts look bigger or smaller. It all depends on what you want.