The Art of the Obvious?

Larry Taunton, in The Grace Effect, lauds Gilbert Highet, author of The Art of Teaching, for his accurate accounting of what a good teacher must have.  To Highet's 'must know the subject, must like the subject and must like the students,' Taunton adds 'must believe in the students,' by which he means believe they can and will succeed.

Taunton points out that

no one believes in a child's capacity to learn as much as her parents.  Most of what a child learns comes via informal (emphasis in original) education; that is, those things that she learns from her parents or extended family.  Whether it involves learning to tie a shoe or how to behave in polite society, parents are the key to a child's education because of their fundamental commitment to their children.  Teachers, curricula, and schools of instruction come and go.  If parents, the only constant throughout the entire process, are missing from the equation, the educational void it creates is incalculable.

If Taunton is right, and I believe he essentially is, then what of those children whose parents don't believe in them, who don't make the fundamental commitment to their children?

We hope, nay expect, the schools to fill the incalculable void.

Is that a reasonable expectation, or is it a misplaced hope?