How do I set up a group log-in?

Here's my situation:

My client sells uniforms to nursing schools students. The school’s instructor provides the students with a password so they can receive discounted prices for specific items. The student would then need to register to make their individual purchase.
Currently, my client has five schools to whom they sell. Each school has specific items (i.e. school crest), as well as general items (blue pants). And, some schools have different prices for the same item, i.e. School A - blue pants #324 cost $24. and School B – blue pants #324 cost $20. I’m thinking of making a different part number for the same item i.e. School A pants are #324 and School B ‘s number is 325. But, I’m not sure how to best to set this up.