This is not purely an Ayu-find but:
It seems that
EXIT TRANCE, Group of DJ's who remix everything from Anime to CM to School songs have made a remix of
卒業写真 ~ Graduation Photo a song which ayu covered as well. Really nice remix ^_^
This song is part of CD
EXIT TRANCE PRESENTS ~Gakko Tance~ Vol. 4 [Aka songs known and popular in Japanese schools, of course with a dancey twist, however there are some that I have heard in my school too~]
I guess this song is used in some schools when people graduate~