The Python IDLE has most of these features (never used the debugger before so I don't know how good it is). It's probably the most minimalist Python IDE out there. See http://docs.python.org/library/idle.html for more. IBM also did an overview of IDLE here.
Also, it's already included in the Windows binary (which is what most schools use, at least here), so you won't have to do any special work to get it up and running. It's available for Linux too.
I've never tried PyScripter before, but it does seem to offer what you need in an IDE and seems fairly simple. Only con is that it's Windows only.
