Sharon McNary believes in having tough teacher evaluations.

But these days, the Memphis principal finds herself rushing to cram in what amounts to 20 times the number of observations previously required for veteran teachers – including those she knows are excellent – sometimes to the detriment of her other duties.

“I don’t think there’s a principal that would say they don’t agree we don’t need a more rigorous evaluation system,” says Ms. McNary, who is president of the Tennessee Principals Association as well as principal at Richland Elementary. “But now it seems that we’ve gone to [the opposite] extreme.”

In New York, which is also beginning to implement a new teacher evaluation system this year, many principals are even less constrained in their opinion.

“There is no evidence that any of this works,” says Carol Burris, a Long Island principal who co-authored an open letter of concern with more than 1,200 other principals in the state. “Our worry is that over time these practices are going to hurt kids and destroy the positive culture of our schools.”

The direction of education reform – and the requirements of the federal government’s Race to the Top competition in particular – means numerous states are now planning to use tough new evaluation systems based at least in part on student growth, tracked by value-added test scores.

But as the first states begin implementing these systems on a broad scale, some are encountering pushback not just from teachers – which is somewhat expected – but from principals and other administrators.

In some cases they question the practicality of the new system, and in others the entire premise on which it’s built. And even a few supporters of rigorous – and high-stakes – teacher evaluations wonder whether rushing them in might backfire.

“It’s something of a Hobson’s choice between rolling out something quickly that’s almost surely going to be flawed in major ways or going about it gradually, and maybe never getting a full implementation,” says Grover “Russ” Whitehurst, director of the Brown Center of Education Policy at the Brookings Institution. “I think there’s a very strong tension between the timetable that works politically … and the practical realities of large-scale reform.”

Tennessee and Florida, both of which are receiving federal funds through Race to the Top, are fully implementing their new evaluation systems this year, and Delaware and North Carolina have most of their models in place. Race to the Top, which awarded $4 billion to 11 states and the District of Columbia in 2010, required the reforms, though it allowed states to choose what sort of system it would use and to determine the timetable.

At the Department of Education, Brad Jupp, a senior adviser on teacher initiatives, says some sort of backlash to changes of this magnitude are inevitable – as are glitches along the way.

“It’s safe to say that when you change people’s work routines in serious ways, they stress,” says Mr. Jupp.

“You’re never going to plan something to perfection,” Jupp says. “Spending time trying to plan things elaborately and building internal support is nowhere near as important as getting things running.”

In Tennessee, the biggest complaint from many principals is simply the amount of time required from them for the new observation system. Veteran teachers, who in the past only needed to be evaluated every five years, now get four observations a year. Untenured teachers need six.

Each observation involves a complicated rubric and scoring system, discussions with the teacher before and afterward, and a written report – a total of perhaps two to four hours for each one, Ms. McNary estimates.

And there are still problems with how the data will be used. For now, many will be judged on school-wide data for reading or math, even if they teach history, art, or physical education – a much-publicized phenomenon that has made the system seem ridiculous in some news stories.

“No one wants to read the headline about the 12th grade physics teacher being evaluated on 9th grade writing scores,” says Sandi Jacobs, vice president at the National Center for Teacher Quality. “That’s not helpful to the cause.”

Still, Tennessee has the basic support of its teacher’s union – even though president Gera Summerford says she has a lot of issues with the implementation of the reforms.

New York, on the other hand, faces a far deeper crisis.

Earlier this month, it was cited by the Department of Education as one of three Race to the Top states lagging on the promises it made in its application (the other two were Florida and Hawaii), in particular due to its problems with the getting new evaluation system in place.

"New York has a chance to be a national leader or a laggard, and we are only interested in supporting real courage and bold leadership," Education Secretary Arne Duncan said in a statement, noting that failure to follow through on its commitments "could cost the state hundreds of millions of dollars for improving New York schools."

A cadre of concerned principals, more than a quarter of all principals statewide, has signed an open letter questioning the wisdom of basing so much on test scores and rushing so quickly.

“I believe in testing. But to use the tests the way they’re being used by the state I don’t think will improve education,” says Katie Zahedi, principal of the Linden Avenue Middle School in Red Hook, New York. She worries that the system will discourage teachers from taking on more challenging students and that it will crowd out any instruction not directly tied to the test.

Chris Brewer, a principal at the rural Morrisville-Eaton Middle High School in Morrisville, N.Y., agrees – and says that the one silver lining has been that opposition over the evaluations has brought together the administration and the teachers’ union in opposition.

At the training he attended on conducting observations in the new system, Mr. Brewer says he was shown a video of an airplane being built in the sky – an analogy for the figure-it-out-as-you-go process educators are now in.

“At the very end, it shows a little kid on this airplane looking out and smiling,” he says.

“But this system has not been tested, has not been tried. I’m not willing to put my kid on board this plane.”

But supporters of the new evaluations say that kids are just who they do care about.

“The status quo in American public education for decades and decades has put all the risk on the students,” says Bill Sanders, a retired University of Tennessee professor and senior research fellow at the SAS Institute. “What we’re talking about now from a policy point of view is how do we balance the risk.”

At the Department of Education, Jupp, for many years a classroom teacher himself, is sympathetic to the fears of teachers and principals like those in New York, and believes their concerns should be taken seriously – but says they need to give the reforms more of a chance.

One thing he’s learned from years of pushing big changes, he says, is that “your worst fears don’t necessarily occur.”

“I don’t think it’s going to be pain-free to move from one era to the next, but I do think it’s a great opportunity for us as a profession.”