Mathias Schulenburg2,679 Points
In determining that max amount of sixth graders, is the teacher assuming that all sixth graders have the same schedule?
Steven Parker203,443 Points
This query is not determining a maximum number of students, but rather a maximum capacity of the rooms that are used for 6th grade classes.
So the final value is based on room capacities and the Students table is not part of the query at all.
We know the students do not have the same schedule, but it would be a different query to determine if the schedules might exceed any of the room capacities. Perhaps you might construct one like that for extra practice!