Many public schools and most private schools require students to wear a uniform. If your child is enrolled at a school with a uniform policy, they will be expected to wear it unless the uniform is optional.
The cost of uniforms varies between schools - some have a casual uniform of a sweater and skirt or trousers, while others have extra clothing like jackets and shirts. In colder climates, there may be both a summer and a winter uniform. Ask the school about this when you visit.
You can usually buy school uniforms at department stores or clothes shops. You can also buy them second hand. Most schools run a second hand shop from the school. Ask your school for advice.