If the course is working with brands then it goes to reason you should be allowed to purchase stock of that isn't it? I did a nail course over 10 years or more ago and we allowed to re stock from the "college shop" which was brands we were practicing or trained with. However once we qualified from college we needed to do each individual product house course if we wished to purchase an opening order with say I had to re do Calgel and Nsi courses in order to buy from them.
But now days many ppl skip that all together and go straight to just do the product or supplier course. So I totally understand where you coming from.
Perhaps try find out if you allowed to stock from college shop or via them first, then you be assured it is genuine.
I do not condone buying off a website that is not the official distributors but I won't lie and say I havnt bcoz I also actually bought off eBay Nsi when I started years ago and had no money (not everyone has the luxury of rich husbands or parents to help them so I know how you feel) and mine was not fake, many people saying it's fake but in reality you have a money back guarantee if it's fake the seller looses their ratings and you get a refund. (I just bought some fake Kylie lips kit cos they sold out on Kyliecosmetics page on line and I got refund from the eBay seller . )
However the dangers are if you misuse or have issues with buying item off line like Amazon or eBay or gumtree or olx etc you run the risk of not having the support of the company itself if something goes wrong or if you have an issue with lifting or something you have nothing to fall back on, as well as insurance I highly doubt will cover you if it's a sale like that. So I would say contact your school first, I have worked with so many acrylics and personally find Nsi to be the nicest (this is my personal pref) and I find it cost effective as it goes a long way and soaks off nicely without too much effort.
But usually most schools do have re stocking kits available to students to complete their case studies and to practice with. I would go speak to them first. As most schools also get a "kick back" from having their student eventually becoming stockist of a said company and you may get a special discount or student starter kit discount. (We did back then but was years ago!)