People in education love to hear stories of teachers who inspire us. But a recent conversation with my staff took a darker turn, as they shared the stories of the teachers who had let them down over the years. These weren't teachers whose behavior was crazy or criminal—quite simply, their teaching was bad.

In my English class we would regularly watch episodes of Seinfeld. The writing was of course clever, but I don't think that was the point. In fact, we were never told what the point was.

One time I went up to my teacher during class to ask a question. She held up her hand to stop me and asked me to wait for a minute. She was trying to count the days until she retired. I know that's what she was doing because she told me!

The English teacher in our school told me that she only had students write about a couple of pages in a quarter, because "it was too hard to grade student writing."

There were never any lectures, discussion, or projects in my freshman biology class. Instead we were told to read the textbook during class. Every two weeks, we'd take a multiple choice test made by the textbook publisher.

In our field, we're loathe to use the term "bad" to describe any teacher, as laden as it is with moral judgments. That was all too evident in the backlash to Cameron Diaz's movie, Bad Teacher, which drew quite an outcry from the field for undermining the teaching profession.

But doesn't the real harm to this profession come when said art imitates real life? And when we fail to do anything about it?

The teachers my staff described weren't fresh-faced novices who were struggling to learn the ropes—such a struggle implies effort. These were teachers, largely veterans, who apparently just didn't care.

Maybe these stories are about teachers from another generation, but I suspect students today could share similar anecdotes. These teachers—while the exception and not the rule—were allowed to keep taking a paycheck home, dragging down their students and placing added burdens on their fellow teachers.

Few school districts ask students about their experiences with their teachers, even though there are now really good instruments that can do so fairly and sensitively. Of the largest 123 districts in the country (the 100 largest plus the largest in each state), only thirteen require or allow student surveys in evaluations of teachers.

Districts also rarely make use of fellow teachers' insights into their colleagues. This sensible evaluation component that unions backed a decade ago hasn't gained steam; in the last few years, consistently only half of large districts allow the use of peer feedback in teacher evaluations. Some districts have backed away altogether, as happened in the District of Columbia.

More often than not, districts cut way back on how often tenured teachers are evaluated. In over half of the large districts we track, tenured teachers can go two to five years between full formal evaluations, as long as their previous evaluation rating was proficient or above—which is how 99 percent of all teachers continue to be rated last I checked.

I know teacher evaluation is now considered toxic, but I've never been one to shy away from tilting at windmills. It's a travesty that we still insist on treating every teacher as equal, when we know that some are exceptional and others are execrable. States and districts have backed away from the very tools that could help us identify teachers who are dialing it in (as well as superstars—but that's the topic of another editorial).

Evaluation isn't a silver bullet, and it doesn't carry much of a bang unless there are some real consequences. But I can't listen to these stories in silence—especially knowing that in some of our nation's schools, stories like these are standard fare, and not the rare exception.