What is the name of the school uniform like in the Japanese manga [summer dress, English style]?

It's called a uniform せいふく

Whether it's high school or junior high school, the school uniform is called a uniform, and the uniforms look different depending on the school

What do you mean by sloppy? The Japanese have said so, what else do you want to do? You're not just asking what that kind of clothing is called, it's called a uniform, right? Uniform! ? What's that? Girls' high school uniforms じょしこうこうせいせいふく！! Are you satisfied?

Isn't that what you said?