OK now in the season 3 episode Moving which is the last episode of season 3 which fans should already know, their was a quote by the adult narrater he say's 13 is a crazy age to young to vote not to young to be in love, something is wrong with that picture, since kevin is done with 8th grade and entering ninth shouden't he be around 14 by the last episode.

no, not if he has a late birthday.

If my bday is in October for example.....then that means that in May/June of my 8th grade graduation, i'd still be 13

Yeah but in the season 2 episode Birthday Boy kevin is turning 13 years old but the school year has not ended yet, in the season 3 episode moving its the last day of school and kevin is still 13 he should be a few months into being 14 years old by that point.

alright so it's an oversight. Not a big deal

The producers must of wanted kevin to be as young as possible in season 3 he is 13 the entire season also in season 4 he is 14 the entire season then finally by season 5 he is 15 and 16 then by season 6 he is 16 and 17, i guess the producers of the show wanted kevin to be as young as possible in seasons 3 and 4 by keeping him the same age for a year.

Yeah he should be about 14 in the moving episode