Random thought but the Snape’s potion class must have sucked for regular students
(His class when he was a student btw, obviously the class he taught sucked too 😂)
So we never learn much about this class besides that Lily was very good at potions but we can make a few assumptions and guesses.
I assume that the gryffindors and slytherins were still together and perhaps NEWT was all the houses together.
Imagine that class… you have Snape who is so good that by NEWT he’s making better potions than the book. You have Lily who is a prodigy too. You have James and Sirius who are the best at pretty much everything. It would be like having four Hermiones AT LEAST in the class. Imagine if all four took NEWTs. You might have a class of like 8 people, with four of them thinking they are absolute failures lmao.
This is kinda head cannon but I can imagine Snape trying to impress Lily or bond with her over potions (or somehow win her back) so perhaps he was trying especially hard. This might be a kind of arms race with James and maybe Sirius too who would not be shown up by Snape. Then Lily just being a good student and naturally gifted at potions. Imagine the competition for the Felix felices?
Sure, maybe James and Sirius would mess around a lot but I get the feeling this might be a lot less as the years went on and they might be more interested in thwarting Snape in these lessons. Plus, I wouldn’t be surprised if they were a bit more into potions given the animagi stuff. I know Lupin says he was never that good at potions but he obviously was the only maurader who wasn’t trying to become an animagus. We don’t know if Harry and James took potions to NEWT but I think they would.
Anyway, just a thought. Slughorn might have had his best ever class.
Edit: don’t forget how Slughorn treats the talented very well and kinda neglects everyone else lol.