Underprivileged students start first grade already two grade levels behind more privileged students. The obvious solution to this discrepancy is to give the underprivileged kids more time, as in another year at the beginning of primary school. That would appear to some to be grade retention (which some do not like), and it would also cost more (which others don’t like), because the underprivileged students would be getting the extra year in school they need.
But, politics intervenes, from all sides. Radical egalitarians, currently a dominant philosophical force in our schools of education, say grade retention is wrong and does not work (ignoring the fact that it works quite well in other countries where mastery is emphasized), and would be happy to deliberately hold the advanced students back until the underprivileged students can catch up. Self-titled education reformers put all responsibility on the teachers–“the single greatest school-based influence on education achievement” (if you count students as not “a school-based factor”). Neither approach is realistic or fair.
There are some impediments to practical education solutions for which both the polar sides in education debates are responsible. But, because the press and policy-makers rarely talk to anyone in the no-man’s-land in between the opposing vested interest groups, they rarely consider the obvious and the practical.