Difference between US and UK English about studying in (a) school

My friend, who is non-native English speaking, lives in an apartment building. He told me that two of his neighbors are American English speakers and three are British.

Sometimes, he asks them for help with English grammar. I am going to write down two similar sentences below that he gave me.

(1) When May and her family moved to Canada, her son studied in elementary school.

(2) When May and her family moved to Canada, her son studied in an elementary school.

He said something like British speakers use an article and American speakers don't OR the other way around. I don't remember which one is which.

Does it really matter? I think without the article, school refers to the level of education. With it, it means the school property itself. Do you think this is an easier way to figure out when to use an article and when not? Please give me your feedback. Thanks a lot.