The problem isn't the teachers' pay. It's the students.
AMEN! Thank you. I've been saying this for years. My job as a teacher would be massively less stressful if it weren't for all those damned teenagers lurking around my desk.
I have always thought these types of systems encourage teachers to teach students to simply score well on particular tests (The standardised tests which teacher's "performance" is based on).
In Texas, student advancement is also tied to the same test. Thus I can, with a clean conscience, really push the kids to do well on their exit-level TAKS tests. The test scores have been steadily improving state-wide, as each year the veteran teachers get better and better at teaching to the test. I'm guilty as a cat with his paw trapped in the canary cage. I mean, I definitely try to teach real history all year round. But the whole school pretty much blocks out 3 weeks of "TAKS prep" each year, as we drill and kill our kids in the subject areas they're to be tested in.
For the rest of the year I do my best to teach critical thinking skills along with the rah-rah patriotism I'm paid to deliver.
One problem with a merit pay system is teachers will avoid difficult school systems. They already have one reason to do that (working conditions), and with merit pay they'd have another (getting paid less than they would at a better school).
Actually just about every merit pay system pays teachers with a "value added" formula. Merit pay is based on how much kids improve their scores year to year compared to each student's
projected improvement rate relative to (a) the previous year's improvements and (2) performance norms demonstrated for all other students in their socio-economic status.
For example, if a white middle class kid in a rural community normally makes a 5% jump in test score performance between 4th and 5th grade, but one teachers' white middle class kids improve by 7%, then that teacher has provided "added value" to those students' educational experience and ought to be rewarded.
Of course the system still sucks. It turns out that if you get your 5th grade students from last years' particularly inept teacher who added no value to her kids' testing, it greatly increases your chance of adding extra value to the normative growth rate of the students--and thus increases your chances of getting a bigger bonus than your fellow 5th grade teachers.
The system is horrible, however I'm getting some of the biggest classroom teacher bonuses in the district, thanks to how the demographic dice roll at my particular school. So I support the corrupt inefficient system cause I got a kid in college and I'm damn poor.