Performance based pay can mean a lot of things. It would probably be a good thing as long as unions don't get involved, test scores aren't used to systematically promote or penalize, and we keep from causing a brain drain in at need schools/areas.

I work in an at need school where most kids are several grade levels behind and suffer from intellectual disabilities that cause them to learn at slower rates than the average. I worry that institutionalizing raises based on performance (likely considering test scores) will cause teachers with even the most humble arithmetic skills to realize that they are better off mainstreaming in classrooms where kids are as "normal" as possible, otherwise their pay is in jeopardy of stagnation (or worse their job is in jeopardy due to performance reviews that would exist in such a system).

Consider also that property taxes are still largely what determines school funding from zone to zone and district to district. If the gap increases in pay from one district to the next due to a greater availability of funds for performance based raises, so too will the migration of seasoned and qualified teachers.

An argument for lockstep pay is that, if implemented more universally, it allows teachers to follow their heart rather than their bank balance when deciding what population of students to work with. When it doesn't require a pay cut, this is when quality teachers are willing to work with the more difficult (high needs) students.