Traditionally we think of the librarian as the primary buyer in the educational market, but there is actually a much larger marketplace out there that writers don't generally think of.
Teachers often have funds to purchase materials for their classroom. Many of them spend their own money.
Counselors, speech teachers, ESOL teacher/coordinators, special education teachers purchase books for their specific needs.
Literacy coaches/Instructional specialists - these are the people within the school who purchase books for classroom libraries and bookrooms. Bookrooms are small libraries set aside usually in a separate room for the specific use of classroom teachers or reading teachers. Books are usually in sets of six copies (6-packs) for use in reading groups.
County level buyers - Homeless coordinator, special education coordinator, instructional specialists, elementary ed coordinator, Title I program directors, grant coordinators. These people will often buy books for every school in their district.
So why do you need to know this as a writer? I want to broaden your horizons. Why do you need to go beyond the question What are my librarian’s needs? In today’s economy, school libraries do not have the funds they once had. Many of them of still buying books, but not in the quantities they once did. There has been a shift in spending in the last few years from the library to the classroom. The books purchased are paperback, rather than library bound, but the quantity of books purchased is much higher.
Here's an example from one elementary school that I serve. It is not a Title I funded school. Orders from Title I funded schools usually reflect the same balance, but they generally have more funds available.
Library order $1,140.35 73 books
Classroom order $4,345.51 728 books
In the list of purchasers above, only one buys library bound books. The publisher makes more money selling library bound books. If you get royalties (a few educational publishers do offer royalties), you make more money on library bound books. But only if they sell.
Realize that the writer has no say in whether your books are published in paperback or not. I just want you to understand that if you’re writing for an educational publisher who does not sell paperbacks, sales are limited because funds are limited.
Many traditional library publishers, who said they would never publish paperback books, are sticking their toes in the water of the classroom market.