Student visa - age limit?

Is there an age limit to the student visa? What if someone much older than the average student age wished to take a year off of their life in their home country and study Japanese at a language school? Would the language school accept them and would they be able to get a student visa?

No, there is no age limit.

There are different categories of student visa, so it depends on which one you are looking at. However, language schools do not have any upper age limits so you should be able to get a visa to go to an established school provided you meet immigration's other requirements.

There are different categories of student visa

There used to be "College student" and "Pre-college student", but they were merged in the changes of 2009. Now there's only one, which is called "Student".

http://www.immi-moj.go.jp/english/newimmiact/koumoku4_english.html

Thanks for the update. And in further reading, it seems there was no age limit on pre-college visas anyway since they included vocational schools.