A number of teachers in our original teacher pool were assistant, ESL, or special education teachers who did not have their own classroom. We removed these teachers from our sample, ending up with 339 teachers in our active teacher sample who participated in random assignment. In the elementary schools, the 163 5th grade teachers, who taught all subjects to the same group of students each day, implemented the intervention with their homeroom students. In the middle schools, the 60 6th ,57 7th , and 59 8th grade teachers were all math specialists and implemented the intervention in each mathematics classes that they taught. In total, the intervention was implemented in a total of 545 distinct mathematics classes.