
A white shirt. Easily bought and cheap. Easy to wash.

A fitted blazer for the girls. Just a option. Fairly cheap. As long as it's black it's fine.

Another example. For girls.

Blazer for boys.

Pencil skirt for girls?

Or pleated?

Trousers. Plain

Black skinny jeans.
You can wear whatever footwear you want. E.g Converse! (^_^)
And maybe ties?