It depends upon the strings. Obviously strings are always attached when taxpayer money is involved. Strings are attached to National Guard funding, interstate funding, business tax breaks, etc. Requiring the money be spent on text books or air conditioned classrooms instead of football uniforms is not an onerous requirement.
The MAGAts want to get rid of the Department of Education and, like you, see it as a federal intrusion instead of a central point of coordination. States band together to buy textbooks since it's cheaper to buy en masse rather than have each state write and publish their own. They're not forced to buy a certain textbook but willfully do so to reduce costs.