NEW YORK – In their zeal for a nationalized education system, Common Core supporters are actually undermining one of the most important education reform policies in recent memory: performance-based teacher evaluations.

It took education reform advocates years to convince enough state lawmakers that a teacher’s job review should be partially linked to how much his or her students are learning – as determined by standardized test scores.

Reform advocates pointed out that teacher evaluation systems based solely on the subjective observations of a school principal were antiquated. Not only that, but reform supporters correctly noted that the outmoded evaluations were the reason that the vast majority of educators were being rated as “effective” – even as student learning declined.

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The teacher unions fought bitterly against this premise, until they realized they were on the wrong side of public opinion. Union leaders then switched to Plan B, which was to minimize the percentage that test scores would comprise in educators’ overall evaluations.

That was how things stood about two years ago.

But now, ordinary Americans are conflating genuine education reform policies with the goals and practices that are part of the Common Core experiment – and they’re opposing all of the above.

A good illustration of this comes from New York, where students in grades three through eight just completed their Common Core testing for the year.

Many parents were already peeved that the testing consumed parts of three school days, ranging from 70 minutes to 180 minutes each day.

Those parents are liable to become even more perturbed when they discover that a significant number of New York principals and teachers believe the Common Core test is poorly designed and probably not worth the effort kids put into them.

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Elizabeth Phillips, an elementary school principal in New York City, explained the tests’ deficiencies in a recent op-ed for the New York Times:

“In general terms, the tests were confusing, developmentally inappropriate and not well aligned with the Common Core standards. The questions were focused on small details in the passages, rather than on overall comprehension, and many were ambiguous. … There was a strong emphasis on questions addressing the structure rather than the meaning of the texts. … And the tests were too long; none of us can figure out why we need to test three days to determine how well a child reads and writes.”

Phillips makes it abundantly clear that her problem is with New York’s test – created by the Pearson company at a cost of $32 million – and the fact that the results will be used to rate the effectiveness of teachers, principals and schools. She explicitly states that her problem is not with Common Core (although it certainly deserves its share of criticism) or standardized testing in general.

Unfortunately, the nuanced position will be lost on the many parents, taxpayers and concerned citizens who see “high stakes testing” as part of the Common Core scheme and want it stopped.

In other words, public opinion is shifting away from performance-based teacher evaluations because of the Common Core phenomenon.

It’s not inconceivable that over the next several years, some state teacher unions and their politician lapdogs will succeed in reinstating the old teacher evaluation systems.

That would be especially ironic, considering that some of the biggest advocates for tougher teacher evaluations – namely, Bill Gates, Jeb Bush and Arne Duncan – are also the biggest supporters of the Common Core experiment.

By overreaching, Gates and company are doing what the nation’s teacher unions couldn’t – and that is to turn ordinary Americans against common sense K-12 reforms.