Collective noun ia a word which refers to a collection of things taken as a whole.
It is definitely not easy to remember them all but it is surely not impossible to learn some of them. You can make it fun for your students such as put up posters about them.
These are some of the examples you can make into posters:
Use these posters on your classroom display board, or as part of whole class teaching activities or for group discussions! You can also ask your students to create their own posters based on other collective nouns. Have fun! - GPSB