How many premade student NPC's is appropriate for a University style setting?

I'm in the midst of creating characters in preparation for DM'ing our group's next campaign sometime in the future, so far, I have created 18 Teacher NPC's. 6 are more minor NPC's, 6-8 are more Major, and the others fall somewhere in-between. I feel quite happy with this spread, although i may want to flesh out the major ones a bit more.

I now need to create the students that will be attending the university alongside the players, but I'm not sure how many is appropriate to make, we have about 6/7 classes represented in our party and I made 2 teachers for each class in our party (and 1 for any class not) but i feel like I should have more students than teachers.

So I was wondering if anyone had any advice on how many student NPC's I should create per class/total.
I feel like 1 or 2 per class as major NPC's works but I feel like I should at least have some extra minor student npc's in each class.

Also to clarify, I will likely add unnamed, background NPC's into the classes to fill them out (I would imagine about 20-30 per class on average, some being a higher range of 30-40, while some being closer to 10-20).