The conservative wing of the GOP pushed Rep. John Kline, R-Minn., the chairman of the House Education Committee, to what amounts to a major watering down of the teacher-evaluation portion of a bill to rewrite the No Child Left Behind Act.

Kline has been very committed to the idea of requiring states and school districts to develop teacher-evaluation systems based on student outcomes—even as his Republican counterpart, Sen. Lamar Alexander, R-Tenn., has argued that it’s not the federal purview. Alexander made teacher evaluations optional under his NCLB reauthorization bill.

But Kline had stood his ground, until today, when he endorsed an amendment by Reps. Rob Bishop, R-Utah, and Steve Scalise, R-La., clarifying that there would be no federal mandate on teacher evaluations under the legislation. In acquiescing, Kline said there was nothing in the amendment that would prevent school districts from doing their own evaluations. But that would essentially take all the teeth out of the provision, education redesign organizations argue.

The National Education Associaton, on the other hand, championed the provision. During floor debate, Bishop argued this would be more workable for schools: “This provides flexibility; it promotes a better outcome,” he said.

House leaders had difficulty wrangling votes for the NCLB rewrite until late last night. It is almost certain that this change helped lawmakers get the votes they will need to pass the bill tomorrow.