I found this article from 2018 that says:

The [union negotiated] thresholds are 24 students for kindergarten classes, 26 for grades 1 to 3, and 28 for grades 4 to 5. For middle and high schools, the thresholds limit how many students teachers may see in a day: 150, or 220 for performance classes, for middle school; and 160, or 225 for performance classes, for high school.