Day/night shift

Day shift, night shift, day school, night school (or evening classes)

@panzade,
Nah Doubt, I asked my Better Half, who is much smarter than I and she agreed, for school not shifts. Instead day, evening and weekend classes

https://www.google.com/#q=Day+or+evening+school+classes+called

Thanks very much Dalehileman and Contrex but here is my problem:

I am translating a study that selected a few classes* in a few schools. First, I have to distinguish between many classes in the same grade. For example, a single school may have as many as ten eleventh-grade classes (not subjects). That would be ~200 students, 20 students per class. In other words, there are 10 home rooms, 10 math classes, 10 history classes, 10 grammar classes, etc., in eleventh grade.

Second, I need to distinguish between shift. Some of those students attend school only in the morning, some only in the afternoon, and some only in the evening (school here is only 5 hours a day). Therefore, some of those ten classes are in the morning, some are in the afternoon, and some are in the evening. To make it clear, students who attend morning classes do not attend afternoon or evening classes. Students who attend afternoon classes, do not attend morning or evening classes. And students who attend evening classes do not attend morning or afternoon classes.

So what is the best way to distinguish them clearly?

Students were selected by ____ (grade class?) and by ____ (shift?).

I am very sorry for making this so long, but I can't think of a more concise explanation.

Shift really is applied to work only. Class-time or "the class-day" or "the school-day" would sound more natural in education settings.

Briefly, two examples, the second if you need to differentiate the grade and individual class:

Students were selected by grade and by class-time (or class-day).
Students were selected by grade and class within grade, and by class-day (or class-time).

You would say:

Morning classes
Afternoon classes
Evening classes

Don't overcomplicate it.