意思上没有区别
知识elementary school是更多用于美式英语（美国人都这么说）
primary school 和 grade school用于英式英语中多一点（新加坡，和英国学校都这么叫）

Grade-school pupils have never had __in the history of the US.答案是this much homework .

so much homework 或that much homework都有可能，that 相当于程度副词so, 但不可能是 this much homework

英语中：小学，校园，怎么说？

primary shcool primary school elementary school grade school