Are you their boss? No principal is going to bad-mouth an employee that they're obligated to work with to anyone who just asks. That'd poison the workplace. They'd be incompetent if they told you their private thoughts!

The evaluation numbers are not public data. But once in the public school district I attended years ago, I got to see the raw teacher scores from in-room evaluations. Because all teachers seemed to put on a 'dog and pony' show the days that evaluators sat in, I was afraid they'd have no correlation with my perceptions the rest of the year.

And yet, while I did not have enough access to perform a detailed analysis, the teachers I thought bad had low evaluations, from both their immediate supervisors and the 'neutral' observers from the district. The ones I thought good had high evaluations.

K-12 teacher competence is not a complicated matter, imperceptible to all but the finest measurements and highly-trained observers. If you're really curious and have the time, ask your district if you can observe the teachers you're most interested in knowing about.

My impression that the quality of services provided by public employees has stagnated or declined is more general than just 'teaching quality'. It's whole-system outputs.

In the school sphere my impression is driven by how the exact same problems and anguish are being expressed today as 10 years ago, 20 years ago, and 30 years ago (which is as far back as I've been paying attention). And roughly all the same quantifiable complaints are being advanced.

Dropout rates remain high – even with rampant under-reporting by state educational departments. When there are occasionally slight improvements in test scores, it's often shown to be due to manipulation of the comparison pools, or nasty tradeoffs to meet hollow numerical targets. And yet, if schools are to be run by large state-oriented (or even worse nation-oriented) bureaucracies, then managing by crude numerical targets are all that's possible.

In the past 30 years, teacher's unions (and other public employees' unions) have risen to become some of the most powerful political groups in each state. Have schools wildly improved over this same period? Are we now in a golden era of public services? Are civil servants now more respected than ever before?

Or perhaps, the 50-year experiment in public-sector unionism has maximized things other than positive results – like off-budget pension obligations and partisanship.