In 2004, the Chicago schools and the union signed an agreement making it easy for a principal to can a non-tenured teacher at the end of the year. How easy? The principal just needed to check a box on a form. You might think that having your job at risk would encourage better behavior on the part of teachers.
Brian Jacob checked it out and found that teachers do respond to having their job on the line, although one could argue about whether the response was large or not.
Many responses are difficult to measure. For payroll reasons, schools track teachers absences carefully. Jacob found that having a job at risk reduced days of absence by about 10 percent. That means the average probationary teacher showed up for school a little less than one more day per year. Definitely some effect at least.
Jacob also found a notable reduction in the number of teachers absent more than 15 days a year.
One final note, the reductions in absences grew after the first year even though the contract didn’t change again. I take this last as evidence that it takes everyone time to adjust to policy changes.