When I was buying school supplies, I'd always shop the sales and buy the least expensive items. No store has a monopoly on the lowest prices, but Walmart says they will match any competitor's printed sale prices.
I bought the fancy pencils at my local "99 Cents Only" store. Some store always has pencils for less than 5 cents each. This year I've seen a package of 24 for $.50. When I needed them, I buy enough for the entire year. I've seen spiral notebooks at Straples for $0.01 each. I buy crayons either right after Christmas, or in the going back to school sales. I bought filler paper for $.35 for a packge of 150. I bought a case of computer/copy paper for $24.99 for a box (10 reams).
When my kids were old enough I give them a clothes budget and give them the money. I told them where the sales were and reminded them they had to buy for the entire school year. Some of my kids spent all their money right away and bought "designer lable" clothes and then cried when they found out they had to wear those clothes over and over again during the year. Some of my other kids saw and learned. They chose to go to Salivation Army, Good Will, and Desseret Industries and paid for their "designer label" and non-"designer lable" clothers there.
Good Luck to you and yours.