When my son was in elementary school, he went to a small private school. Their supply lists were two to three times longer than the public school's lists. And all year long the school was looking for lots of other things to make costumes and projects for whatever they were studying.
I never minded the cost. I felt he was getting a much higher than average education and everything they called for, was used.
I'm guessing in a lot of the public schools, the lists are longer now because so many kids don't bring in their own supplies.
It seems to me like all areas now have a 'stuff the bus' or 'fill the backpack' programs and there really isn't any excuse for teachers to have to dip into their meager salaries to buy basic supplies.
Basic school supplies go on sale so cheaply at the beginning of the year, there is no excuse for parents not buying enough for the whole year. Here tablets are sometime $0.09 (yes, nine cents), packs of pencils .25 to .50, glue sticks .25 to.50 per pack, crayons and colored pencils at .25 to $1 depending on brand and size, paper folders just a few cents each, etc.
Even when the lists call for things like tissues, they can be had for under $1 per box
Some of the high end calculator and things for high school get pretty pricey and I can see people having trouble affording those things.
But there really isn't any excuse for not having the basics.