I must be punctual for class.

我得准时去上课。

youdao

I have to go now because I must be punctual for class.

我现在不得不走了，因为我得准时去上课。

youdao

You may be punctual for work (barely) but you're usually at least 20 minutes late for meetings, appointments, class, church, theater or other non-work situations.

可能上班的时候，你勉强能做到准时；但在会议、预约、上课、教堂、剧院及其他非工作场合，你通常都会迟到至少20分钟。

youdao