Note: Celine Coggins, founder and CEO of Teach Plus, is guest blogging this week.

There’s a fascinating and very worthwhile teacher quality debate that’s happening in the blogosphere right now (see Rotherham versus Weingarten and Hanushek versus Ravitch). Hanushek suggests, based on economic analyses of student test score data, that up to 400,000 teachers (up to 10% of a 4-million-person workforce) should be fired. That number is scary and high for anyone who has many individual teachers in their lives whom they care about.

Because Hanushek’s figure is based only on test score data, it is open to some easy criticisms. The first is that test scores, themselves, are insufficient to give a complete picture of a teacher’s value to students. For me, an economic analysis conjures a cold image of faceless teachers lined up Hands-Across-America style, from best to worst. I think everyone agrees this is neither possible nor desirable.

The second criticism is that many teachers at the lower end of the spectrum could improve if given greater support. As increasingly resource-starved districts increase teacher workloads and cut supports and development, many teachers who could improve aren’t being given a fighting chance to do so.

Finally, the unions, who are appropriately concerned about the size of the population on the proposed chopping block, point out that they have taken major strides of late to expedite the dismissal of persistently weak teachers.

In my view, this conversation is suffering from 35,000-foot syndrome. In the policy world, there appears to be a fixation on the anonymous “bottom quartile of teachers,” with too few examples of the texture of the challenges we face within this group. Weak value-added scores are a symptom of the problem, not the problem itself. It’s easy to talk about teachers and their test scores. It is more difficult to talk about the varied reasons that explain those scores.

There is inspiring work happening all around the country right now to help our field get a clearer picture of what mastery looks like in teaching--and how teachers can be coached toward it. I believe the gospel of teacher effectiveness, so prevalent today, is driving the right conversation about what good teaching looks like and the power of teachers to change the lives of children.

Yet, I’m reminded of how “teacher quality” was framed in the late ‘90s. The focus then was on “a competent and caring teacher for every child.” I believe that phrase--as weighted toward the qualitative, as effectiveness is toward the quantifiable--is still relevant too. Let me explain why from my vantage point.

At Teach Plus, the central question of our work is: What can we do to help excellent teachers extend their commitment to urban classrooms?

In surveys of teachers in regions across the country and in countless conversations, teachers tell us that colleagues are their most important working condition. It is their colleagues who help them determine whether they feel like they are part of a high-caliber, deeply-meaningful profession--or not. Colleagues are central to the “stay or leave” decision of strong teachers.

When they talk about colleagues in need of improvement, they don’t tend to talk about value-added scores. Instead, they wrestle with real cases of practice that raise good questions about what our baseline for “caring and competence” should be.

Here are a few examples of statements teachers have overheard being taught to students:
• A right angle is an angle that points to the right.
• Alaska is in a box on the map because it is too big to fit otherwise.
• “Indivisible” in the Pledge of Allegiance means “cannot be seen.”

Each challenges us to better define baseline competence.* If certification tests of basic skills are not picking these things up, should we assume they’ll be picked up in a new souped-up evaluation process? How many promising, able teachers (the teachers at the other end of the spectrum) do we lose when teaching is not treated as intellectual work?

And what about a baseline for caring? Ask a female teacher who had to physically restrain a male student after school hours as other teachers walked by her on their way out the door. She’d tell you the bar for what constitutes a caring professional is unclear.

How would we remediate these challenges? Is it possible? In many cases the answer should be “no,” not simply because test scores are low but because the profession enforces certain standards for teacher practice and knowledge. This is the conversation we need to be having if we really expect to move the needle on the quality of the teaching force.

*I recognize these are one-off examples used as an illustration. I’m making the perhaps inaccurate assumption that knowledge gaps like these are akin to speeding. There are a thousand infractions for every time you get caught.

--Celine Coggins