What grade were Beaver and his class mates? Beaver was supposed to be around 11 right. Is that the right? So about 4th grade. US history was taught in 5th grade and 11th grade when I was in school where I was. The point of the show was of course that you should do all your school projects on your own.

Beaver was in the fifth grade for this episode. He had Miss Landers for three grades and this was the last year.

That makes since. It’s the last grade that they had Miss Landers.

Right, the next season he was supposedly in the sixth grade. Toward the end of the that fifth season, they stopped mentioning his grade, until in the last few episodes, Wally made a comment to June that Beaver was going into the eighth grade.

In other words, they got him into the grade sequence he should have been in, in the show. Eighth grade Beaver in the sixth season would have him on the path to graduate high school in 1967, just as real-life Jerry Mathers did.

So, in season 1 Beaver should have been in the third grade (and Wally should have been in the seventh grade, but that's another error.)