There should be a grad after grade 12 not 8 becasue you still got school after grade 8.
Well, benben714 is *sorta* right...it symbolizes going from middle school (at least in the states) to high school, which is much different.
Some places even have pre-school graduation, kindergarten graduation, elementary school graduation, middle school graduation AND high school graduation. It's just to symbolize moving up to the next tier of education / schooling. (Speaking for the US).
Yeah here in Canada where i am we have Elementary School which is K-8 in most cases, and then high school which is 9-12, so there is a graduation to symbolize the achivements in Elementary and then again at the end of highschool
there is graduation after grade 8 because it symbolizes you moving from elementary school onto highschool
where i live in ontario, we also have graduation after grade 12 because this is your final highschool year