我们学校和他们学校是姐妹学校.

Ours and theirs are sister schools.

我听说这次旅行是去拜访我们在波士顿的姐妹学校。

I heard the trip was to visit our sister school in Boston.

所以我们有汉语课。（姐妹学校？）

So we have Chinese(sister school?)lessons.

所以我们有汉语课。（姐妹学校？）

So we have Chinese(sister school? )lessons.