What age should a kid start wearing a?

Well, it depends. Lets say if you were 9, and you needed to start wearing bras. Start off with a training bra. Start off with those because they're more comfortable and not as tight as normal bras. If your 'things' are starting to grow earlier than people in school, that's alright. I'm the only one in my class that wears a bra ( 3rd, 4th, and 5th grade is when girls usually start changing ) but if you start of late, that's alright also. You will start to want to wear a bra near 5th-6th grade because in 6th you have to change for gym class and most girls wear them by then.