The law was probably not drafted by an English teacher.  What does the final phrase "used by the eligible educator in the classroom" modify, anyway?  Just "supplementary materials," or the whole laundry list?  And it's like an afterthought to the first category, which involves continuing teacher education.   

§62(a)(2)(D) Certain expenses of elementary and secondary school teachers
The deductions allowed by section 162 which consist of expenses, not in excess of $250, paid or incurred by an eligible educator—
(i)by reason of the participation of the educator in professional development courses related to the curriculum in which the educator provides instruction or to the students for which the educator provides instruction, and
(ii)in connection with books, supplies (other than nonathletic supplies for courses of instruction in health or physical education), computer equipment (including related software and services) and other equipment, and supplementary materials used by the eligible educator in the classroom.