Was it common back then for 12 year olds to be in 8th grade? Wally was 12 & so was Tony during the the 1st season (12-13). He would probably have been in 7th grade. Why Beaver so young 7.75 years old in comparison to Jerry’s age would have been when filming and airing began? He would have been 9 & in about 4th grade the fall the Leave it to Beaver started. The writers wanted them to be about 3 years apart which would worked with the actors proper age and grade level or had Wally in 7th grade and Beaver in 3rd or 4th grade. The writers also seemed to dumb down Beaver’s age and he would been treating girls in the later seasons, which when his acting seemed to slip.