Dwayne was a year behind Raj and Rerun in school, so why...

Good point, maybe Dwayne was "advanced"? I could easily believe that Rerun was behind, but not Raj, so there goes that theory. But I remember, going as far back as elementary school, a kid or two from a lower grade joining our class for English, and in high school, math classes seemed pretty mixed.

It's high school, when I went to high school there could be people from 10th, 11th, or 12th grade all in the same class.

Maybe not. It could be Dwayne was in Advanced History with Rerun and Raj.

I don't know how it is now but when I was in school it was very common to have kids of different grade levels in the same class, especially with elective courses or courses that are chosen by the students but not required (e.g, drama, foreign languages, PE, art, home economics, etc.).

It could be an AP class, whereas the underclassman is already ahead of their required course and to avoid repeating the course, take the same course on an advanced level.

Then their could be a case whereas an underclassman decides to take all of their required courses or courses needed to graduate, first and wait until their senior year to take their elective courses. At the same time a senior may have decided to do the opposite and take their elective courses first and have to take their required subjects their senior year in order to graduate, thereby causing the two to have the same classes.

Don't Worry Be Happy.

I wondered the same thing! I'm surprised many people replied that it was common in their high school to mix the grades! Huh? Then what is the point of even HAVING different grades?

In my school, If a student in 10th grade was "advanced" in Math (or ANY subject, but let's use math as an example here) that student would be put in TENTH GRADE honors math! Not 11th grade honors math. There was no jumping a grade. They'd be put in all the honors classes for their DESIGNATED grade.

The only classes my high school had that mixed grades were Study Hall, Art, Computer classes, Music or any of those elective classes that weren't grade-specific. Academic classes were never mixed. If you were smart, you remained in your grade and were just put in THAT grade's honors classes.

OR if you failed a class, you had to REPEAT it with the lower grade. Like if you failed 10th grade Math, they made you take it again in 11th grade, but you'd remain in the 10th grade Math class.

When I was in HS, I sat in with a higher grade's math class. I was good at math.