Even if you do have a state sales tax exemption, that only applies to items you purchase for your exempt purpose. So, if you bought any books for the library or classrooms, those would be exempt from sales tax, but otherwise, as pan01801 said, you're a reseller.
There are some exceptions to this, but the general rule is that you keep about 50% of the sales at a Scholastic Book Fair. There are some variations depending on how many book fairs you have, other bonus programs Scholastic has, whether you take your profit in cash or Scholastic dollars.
In Texas, sales-tax-exempt non-profits can host two days of tax-free fundraisers. So it's important first to know WHAT is taxable. Not everything is, so if you pick something just because it is a large fundraiser, but it wasn't a taxable activity to start with - you've wasted your freebie.
The State Comptroller's Office has been making an effort lately to clarify that activities where the non-profit acts as a sales agent are not eligble as one of the two days. So if we buy something, take all the profit/loss risk, and re-sell it, then it qualifies. If we sell something for a % of the profits, then it doesn't.
That was a huge shocker for us as we had always counted our big fundraiser of cookie dough/gift wrap, etc. which was apparently an incorrect practice.
We do charge sales tax to the parents for Scholastic Book Fairs.
It is confusing (Tim it would be great if you could confirm)
Someone researched it a few years ago, and as I understand it, if you do not have state tax exemption status (which is a separate filing in MA for non profit) you are subject to sales taxes. Essentially you are acting as a Reseller of Books (regardless of how you take the profit) you are still selling books (taxable item)
Our school holds bookfair, with PTO members sitting in during the sale. The secretary has us round of the price of a book ($3.95 would be $4) to help cover tax.
Never really thought about it, but that is just how she has us do it.