LOL... depends on how much you like what they do! I usually tip better than average for this stuff from what I hear so not sure you'll like what I say. Specially at the beauty school. I'm warped, I'll go there for the best price and then tip the same thing I pay.
At present my boss' stepdaughter is going through the cosmotology school. For entmoot she wanted to bless me with the gift of a pedicure. A VERY nice one! I thought that was so sweet! She's struggling to get through school with 20 month old twins after their dad walked out and she's gifting me with a pedicure. Left her a $20 anonymous tip in her equipment tray. Her mom says she thinks it was me but can't be sure... I didn't admit nothin'! :-)
At my nail salon I usually leave her $5. But, I watch everyone else and they usually leave $1 or $2 so I think that is prolly normal. $1 per item shows that you appreciate 'em.