I don't follow your objection. Banning books on sexuality from public schools threatens sexual education in those same schools. That is true even if individual parents can purchase such books for their children on the open market.
The point of universal education is to provide for all students, _especially_ those whose parents are unwilling or unable to provide a quality education independently.
The point is that decisions made by schools about which books they use or not are not equal to legally enforceable book bans for the general public. The article commingles these two ideas. That is the objection.
The snippet you quoted does not support that objection, though. It is clear from context that the "book bans" referred to are in the realm of public education.
The point of universal education is to provide for all students, _especially_ those whose parents are unwilling or unable to provide a quality education independently.