What does it mean?
During my primary school years my teachers used to focus briefly on certain dates across the year, the winter solstice (June 21 here), the autumn equinox (Mar 21) and the Spring equinox (Sep 21) were but a few.

In Yr 3 I remember reading a story about a Priest, Griffin and a boy.
I don't recall the plot exactly, but for the purposes of the story the Griffin only ate each equinox, and then the meal was a little boy.
I think th boy became a friend of the Griffin; the Priest's role is what I don't remember, and being a children's story I think the Griffin remarked that his said repast was something fictitious.

Who has some Myths, pagan or otherwise relating to the Equinox?

i don't know, but i found it interesting !!

lol, what kind of a school did you visit ?