(a) In this section:
(1) “Backpack” means a messenger bag, book bag, or a pack with straps that a person wears on the person’s back, including a backpack with wheels if the backpack can also be worn on the back. The term does not include an item that is commonly considered luggage, a briefcase, an athletic bag, a duffle bag, a gym bag, a computer bag, a purse, or a framed backpack.
(2) “School supply” has the meaning assigned by the Streamlined Sales and Use Tax Agreement adopted November 12, 2002, including all amendments made to the agreement on or before December 14, 2006.
(a-1) The sale or storage, use, or other consumption of a school supply or a school backpack is exempted from the taxes imposed by this chapter if the school supply or backpack is purchased:
(1) for use by a student in a public or private elementary or secondary school;
(2) during the period described by § 151.326(a)(2); and
(3) for a sales price of less than $100.

(b) A retailer is not required to obtain an exemption certificate stating that school supplies or school backpacks are purchased for use by students in a public or private elementary or secondary school unless the school supplies or backpacks are purchased in a quantity that indicates that the school supplies or backpacks are not purchased for use by students in a public or private elementary or secondary school.