I just had a phone interview with a college. I think it went pretty well. Should I now send them an email just saying thank you for your time etc. or is this overkill? I know that the thank you email is customary with job interviews, but is it needed for college?
I would, yes.
@medrunner1998 - yes please send a thank you note. Those are always appreciated, but not needed per se. And don’t expect a reply.
YES!
My husband does not invite any job candidate for a follow-up interview if he receives no thank you note – or email – after the first.
I know that’s for a job, but college interviews follow a similar etiquette.
Always send a thank you, it is polite and it let’s them know you are as well. And, it’s just the right thing to do.
It never hurts to send a thank you note. It is customary to do so for a college interview.
And if you really want to impress the interviewer, send a hand-written note through the mail. 
You may not have an address to do so, however, in which case email is fine. A short/sweet “thank you so much for taking the time to talk with me, I enjoyed our conversation very much” sort of thing is fine.
I had a few alumni interviews and an official campus interview, and I didn’t send thank-you emails to any of them.
At the end of the interviews I thanked them, which I thought was enough.
Definitely send a prompt thank you. I also highly recommend a written thank you note. My daughter has done this after every interview and on-campus meeting (eg. coaches & professors who spent time with her). More than one responded to her thanking her for the kind card, both in email and in a written note in the mail later.
Good manners are always the right thing to do.