I am a lovely middle school girl.

我是一个可爱的女中学生。

She's a typical "high school girl".

她是高中女生的一个典型代表。

Especially that pitiful little school girl!

尤其是那个可怜的小女生！

I can do things that a normal school girl can't do.

我能做的事情，一个普通学校女孩不能做。

The proposal you write is worse than school girl level.

你写的方案还不如我念小学的女儿。