He had spent the entire night in the classroom working on a mathematics puzzle.

他在教室里带了一整晚，钻研一道数学难题。

Here's his portfolio, if you want to take a look at his classroom work.

如果你想看看他的课堂作业，这是他的作品集。

The training includes extensive classroom work in such subjects as first aid and passenger psychology --- as well as practical training in flight procedures and meal service.

培训包括广泛的课堂作业，如急救和乘客心理学等科目，以及飞行程序和膳食服务方面的实践培训。