Our school has lessons with 4 week and lessons with 2 week cycle

First you have to specify that your timetable has 4 weeks:

How can I define weeks?

Then you have to create som week combinations:

Combine Weeks A and C together to create Even Week
Combine Weeks B and D together to create Odd Week

Select two weeks, press button combine and choose first option:

Then for each lesson you will be able to say that lessons in for example in Week A or in Even Week, which will place the lesson on the same position in both Week A and Week C.