As I said, I'm quite puzzled by the the teachers instructions, but In making 4 patches I guess it really doesn't matter what size squares you start with as long as you're consistent throughout and the whole quilt is made up of the same size four patches. I think we always think in terms of an even measurement for the finished block plus 1/4" all around for seaming, but with this, any size is O.K.
So, Sondra, if you want to go ahead and work on a simple 4 patch quilt, I say make a whole lot of four patches , using whatever method and size you're comfortable with and join them together or alternate them with same size plain squares and you'll have a nice quilt in no time.
Play around with your fabric and it may all come back to you in a flash. It's only fabric and there are no Quilt Police out there.