Even though 16 to 18 states have back-to-school sales tax breaks and retailers are offering big sales for families, the National Education Association still recently estimated that the cost of back-to-school supplies has risen by as much as 42% this year.

While some have gone up as little as 17%, other essential items have risen by over 40% of their previous costs. Families will spend an estimated average of $922 per student on school supplies this fall, 47% more than last year, according to PricewaterhouseCoopers, putting substantial strain on parents with multiple children. Just sending two children to school can cost as much as $1,844 out of pocket, causing a steep rise in what’s known as the “backpack tax.” That’s far from the “free” moniker often assigned to public education, exposing the truth hidden behind the cost-free label.