More than a decade ago, Denver teachers pushed for a pay-for-performance compensation system. Now, educators are going on strike in order to get rid of this system because it has caused numerous “unintended consequences.” This payment system has resulted in stagnant wages and increased testing of students in order to determine educator performance. Laws have shifted away from this type of performance/compensation system, and now teachers whose wages are not as high as they would like are also attempting to do away with this system by going on strike.
See "Denver Teachers Once Hailed Performance-Based Pay. Now They’re on Strike Over It.", Julie Turkewitz & Dana Goldstein, The New York Times, February 11, 2019