Do not print some breaks or periods in some classes (or teachers or in summary timetables)

For each period or break you can specify, that it shall be printed in only in a group of classes. If you for example have a different breaks in grades 5,6 and in grades 7,8 you can add two breaks and set two sets of bells.
At first - please, see this article how to define different bells for groups of classes:
We have different recess times in parts of school. How to input it? (Solution 2).

Then for the first break set that it shall only be printed in "Bell 1" - it means only in classes in 5th and 6th grade. Then do the similar with the second break - define that it shall be printed only in the "Bell 2" classes (so grade 7th and 8th).

And that's it...Now, if you check the printouts, you will see, that there will be always only one break but on different positions.