I was just talking with a middle school teacher yesterday about the new version of Google Sheets. We both tried it, but found ourselves reverting back to the "old" version because of the lack of script support. But I just came across this article from Lifehacker this morning that gives me a couple good reasons to try the new version for some things. Google has just launch "add-ons" for both sheets and docs. Check out this Lifehacker article to see if any of the initial "add-ons" intrigue you.
I had a teacher ask me if there was a way to hide or remove students who are no longer in your class. The answer is maybe. It depends on if they are officially dropped from your class and appearing as red in your roster and gradebook. If not, then no, you cannot remove them until they have been unenrolled from the class. If the student is showing up as red in your gradebook though, you can hide them so you don't have to worry about them. Here is a screenshot to help you do it: