I attended a smaller private school for junior high and while they didn't have a uniform they did have a strict dress code.
All the boys had to wear long pants either jeans or khakis, a button down shirt or polo with a collar, a belt, and tennis shoes or dress shoes. Your shirt had to be tucked in at all times as well and your shirt could only have the first two buttons unbuttoned.
All the girls had to wear a dress or skirt with a button down blouse. The skirt or dress had to be knee length or longer and either tennis shoes or dress shoes were required for the girls as well.
So needless to say I wore a lot of Levi jeans, Nike or generic dress shoes, and whatever shirts my mom could find at Kohls.