big, large
small
advanced, beginners' (BrE), beginning (AmE), elementary, intermediate, introductory, remedial
master (usually masterclass)
biology, history, etc.
acting, creative-writing, dance (AmE), dancing (BrE), etc.
evening, night (esp. AmE)
college, high-school, kindergarten, undergraduate (all AmE)
entering, incoming (= the students starting a school or college in a particular year)

attend, go to, take
He's taking classes in pottery.

enrol/enroll in, sign up for
cut (AmE), miss, skip (AmE)
disrupt, interrupt
hold
The institute holds evening classes throughout the year.

offer
The college offers classes in many subjects.

conduct, give, lead (AmE), run (esp. AmE), take, teach
Who's taking the class today?

address
dismiss
Class dismissed!

fail, flunk (both AmE)
pass (AmE)
ace (AmE,informal)
drop
cover
observe, sit in on

be easy, be hard
be available
graduate (AmE)

member, teacher
size
discussion
work
reunion
schedule (AmE)
period (AmE)

in (a/the) class
We'll start the exercise in class.
Which history class are you in?

class in
She's going to evening classes in Italian.

the back of the class, the front of the class
He sat at the back of the class.

be top of the class, come top of the class
She came top of the class in English.

the class of … (= a group of students who finish their studies in a particular year)
the class of 2008

the entire class, the whole class

leisure (= rich people), lower, lower-middle, middle, upper, upper-middle, working
sections of the working class

chattering (BrE), educated, elite, governing, political, privileged, professional, ruling, wealthy
topics being discussed at the breakfast tables of the chattering classes

capitalist, entrepreneurial, merchant
labouring/laboring, peasant
landed, landowning
dominant
social, socio-economic
Membership of the club is drawn from all social classes.

structure, system
consciousness
interests
conflict, differences, divisions, struggle, war, warfare
issue

large, small
distinct
special
rare
age, weight

constitute, form
These writers form a distinct class in Russian literature.

class of
a rare class of neurological diseases

be in a class of your own, be in a different class (= to be much better than others)

great, real
a player of great class

have
She has real class.

a touch of class
The musical entertainment added a touch of class to the occasion.