At my local Rite Aid, most of the school supplies are 50% off right now, as the stores try to make room for Halloween candy and decorations.
The same is true at Target stores. And though I haven't personally checked out CVS and Walgreens, it's likely they're having similar sales.
So, here's my advice. Stock up on school supply staples, like pens, pencils, folders, notebooks and binders now.
I don't know about your kids, but mine always seem to need new binders about half-way through the school year, when the rings get bent out of shape and they won't close anymore.
And what they don't use this year, you can always have for next year, or for charity "fill-the-backpack" drives.