Education is not simply the responsibility of the teachers. There are many issues outside of the control of teachers that effect the performance of the children in their classroom, specifically
disruptive and rowdy children
parents that do not interact with the children and homework
diet
attendance
among others.
If we are to get the education system on track in this country both parties need to be given a vested interest in the children of this country performing well. If we are going to give a significant tax credit to parents simply for having children, I believe it is reasonable to measure the amount of that tax credit based on their performance as parents, as measured by preparing their child to be a productive educated member of society.