Question

Does a comma go after an independent clause with a subordinate conjunction followed by another independent clause?

Example
The classes will be held unless the schedule has been changed.

I know one is needed if a dependent clause is first.

Answer 1

A comma is not needed here.

Answer 2

There is not universal agreement about comma usages. However, I'm of the school that says, "If in doubt, leave it out."

Answer 3

Ms. Sue is right. There is no comma needed in your sentence.

Here's a well written webpage explaining the comma rules, with examples:
http://grammar.ccc.commnet.edu/grammar/commas.htm

Be sure you check them all out!