In a new study, Hoover Institution researchers found that uncertified teachers perform just as well as certified teachers. Where have I heard that before?

This quote says it all: But researchers said the study results showed that school systems, instead of focusing on whether and how teachers are certified before hiring, should worry more about getting rid of teachers who perform badly during probationary periods.

Without certification restrictions, school districts would be able to get rid of bad teachers without worrying about finding enough certified teachers to meet their state-enforced quota. Throw in a merit pay system and you are in business.