One obvious fact that you seem determined to ignore...over the last 10-15 years, Branstad and Reynolds have not fully funded education in the State.
That causes local districts to cut teaching positions to meet budgets. That results in larger class sizes. That results in less assistance to students. That results in lower test scores. That, in turn, allows Iowa's Governor to claim public schools are failing.
Republicans are all for cutting taxes. Republicans in Iowa have seldom prioritized supporting students other than these theatrical claims of curriculum selection.