The "unschooling" movement of the 1970s featured open classrooms, in which children studied what they were most interested in, when they felt ready. That was followed by today's back-to-basics, early-start model, in which students complete math worksheets in kindergarten and are supposed to take algebra by eighth grade at the latest. Under the "whole language" philosophy of the 1980s, children were expected to learn to read by having books read to them. By the late 1990s, reading lessons were dominated by phonics, with little time spent on the joys of what reading is all about — unlocking the world of stories and information.

A little more than a decade ago, educators bore no responsibility for their students' failure; it was considered the fault of the students, their parents and unequal social circumstances. Now schools are held liable for whether students learn, regardless of the students' lack of effort or previous preparation, and are held solely accountable for reaching unrealistic goals of achievement.

No wonder schools have a chronic case of educational whiplash. If there's a single aspect of schooling that ought to end, it's the decades of abrupt and destructive swings from one extreme to another. There is no magic in the magic-bullet approach to learning. Charters are neither evil nor saviors; they can be a useful complement to public schools, but they have not blazed a sure-fire path to student achievement. Decreeing that all students will be proficient in math and reading by 2014 hasn't moved us dramatically closer to the mark.

Now consider the latest rush to extremes: teacher evaluations. In its effort to promote school reform with Race to the Top grants, the Obama administration rightly criticized state laws — such as one then in effect in California — that prohibited schools from making student test scores a part of teache