A Question for Teachers Unions

Here's something I've been meaning to ask my teachers union friends in the edublogosphere: Why do you support tying salary increases to Master's degrees, when all the research says that Master's degrees do your members no good?

It makes a certain kind of sense for unions to support things like seniority raises, tenure, bumping rights, generous retirement benefits, etc. I may not agree with the union position on all of these issues, but the union position is at least rational from the perspective of representing the interests of some or all union members.

Master's degrees are different. Teachers get those other benefits automatically in return for doing their job. Master's degrees exact a significant cost from teachers, both in time and money. To get one, you have to pay tuition, go to class, and spend a lot of nights and weekends away from your family. Since teachers don't get paid very well and many of them have children, these costs are considerable.

Yet if there's one thing that all the research studies out there agree on, it's that there is no relationship between having a Master's degree and classroom effectivenes. In fact, the latest large-scale study on the issue found--incredibly--that teachers who go back to get a Master's degree after starting teaching are actually less effective than those who don't. From "How and Why Do Teacher Credentials Matter for Student Achievement?" by Clotfelder, Ladd, and Vigdor:

The estimates indicate that the teachers who received their [Master's] degree prior to entering teaching or any time during the first five years of teachers were no less or no more effective than other teachers in raising student achievement. In contrast, those who earned their master’s degree more than five years after they started teaching appear to be somewhat less effective on average than those who do not have master’s degrees. Whether this negative effect means that those who seek master’s degrees at that stage in their career are less effective teachers in general or whether having a master’s degree makes them less effective cannot be discerned with complete confidence from this analysis. The observation that the earlier master’s degree has no effect, however, suggests that the negative sign is more attributable to who selects into that category than to any negative effect of the degree itself.

So Master's degrees either reward teachers who were already worse, or they make them worse.

Given this, why don't unions go to bargaining table and/or state legislature and change the salary schedule so that all the money that currently goes to support salary bumps for Master's degrees ($8.5 billion nationwide according to this estimate) is reallocated for other purposes, like increased minimum salaries, lower health insurance co-pays, or what have you? That would be a net gain for union members, because they wouldn't have to expend the time and money that Master's degrees require.

Alternatively, why don't unions go to the local university--I'm guessing that for any given school district, most in-service master's degrees are earned at relatively small number of local colleges and universities--and say something along the lines of "Hey, in exchange for our time and money, could you give us something that actually helps us be better teachers?"

Leo Casey? AFTie John? Anyone?