At the Huffington Post, Jaime Hudgins writes:

Richwine and Biggs hint at performance pay in their Room for
Debate commentary, and another commentator,
Lisa Snell from the Reason Foundation, points
out that the National Education Association, the
nation’s largest teachers union, “calls for differentiating teacher
compensation based on teacher effectiveness, the roles that
teachers play, the difficulty of teaching assignments, and the
length of the school year or school day.” Of course, the
development of criteria for determining which educators are deemed
“effective,” and which are best suited for leadership roles, is
complicated. There is no single definition of what is, or makes, a
great teacher.

Full column here. 

Reason’s education
work is here.