The way I saved on clothing was that I bought clothes off the clearance racks at the end of every season and saved them until the next year. I don't think there was ever a year that the next size up didn't work for either one of my kids. I supplemented with the thrift store. That way, they had new clothes but they also had a decent amount of them. I don't remember them ever complaining.
I also bought a lot of school supplies the year before whenever I was at a store that had certain things for next to nothing, so I never had to spend a ton on supplies.
What can you do if you haven't shopped ahead and need things now? Here are some tips:
1. Look at the flyers of stores you regularly go to (and maybe some you don't) and find different things they have on sale. You can find crayons and markers at one, folders and tablets at another. This does take some running around, and you have to decide if the gas and time spent are worth it, but if you are taking a day for back to school shopping anyway and these stores are close to each other, it may be well worth your time.
2. If your kids are fussy and/or you simply want to provide them with new clothes, you may have to get the new things at an inexpensive place like Wal-Mart. Then, after you purchase a modest amount, just so they can have something new, you could go around to a number of thrift stores. Some people are afraid of thrift stores but I am not by any means! You can find amazing things there, better quality than Wal-mart and sometimes even brand new! If your kids don't want to go and browse, I would suggest doing it yourself. You can buy a few things you think they will like and return them if they don't.
3. Garage sales are still going on and you might find a few things there.
All in all, back to school doesn't have to cost a fortune. It always will take a bit of a bite, especially with the school fees. A good thing to remember too, is when you are buying those great deals from store to store to pick up enough for next year too, if you can, and know you have planned well ahead. If you do this every year, and get ahead of the curve, even if you have a very skinny year financially, you will know ahead of time your kids will be well stocked.