KLASSE means "class" as you may have guessed. It's also used when you're impressed with something, in the sense that it's "great" or "class". Great lingo to use if you're a footballer: "Das ist klasse!"..."That's great."

But be careful as KLASSE in an educational sense only refers to a classroom. An actual lesson, which we might call "a class", is STUNDE, which means an "hour" in English. But German being sometimes such a straightforward language, LERNEN means "to learn" and LEHRER is "teacher" and LEHRLING is a "pupil". So whereas English uses a number of different words, German has the same root.

But before you think I'm giving German an easy ride, then you've got the word UNTERRICHT, which means "teaching" or "instruction".