"class periods" is correct and usable in written English.
It is typically used to refer to the sections of a school day. For example: "All of the students were well-prepared for the upcoming class periods."
Getting through the day, the nine class periods.
How many class periods could you have sat through?
Every piece of creative writing was recorded, an activity that ate up entire class periods.
I allowed four class periods (about four hours) for this project to be completed.
Other educators agreed, however, that turning the focus of some class periods to the testing material came at a price.
There, the teachers had to squeeze 40-minute classes into 26 minutes due to shortened class periods.
In recent years, the district has also extended math and language class periods to 90 minutes for more intensive instruction.
The additional minutes were spread over the entire week by increasing class periods by less than five minutes each.
If time and resources are available, students may film and then screen their movie shorts in future class periods.
In Elizabeth, children, including kindergartners, will spend six class periods learning, among other things, the difference between telling and tattling.
I expect this lesson to take one-two weeks of class time, in 45-minute class periods.
