Aw yeah! More schoolroom smuttiness from my favorite pair! This was really fun! Glad you were inspired to do more quickly!
As for suggestions: I'd like to see more consistent perspective -- it bounces back and forth between the two pretty quickly, to the point where I'm not sure at the beginning of the sentence if we're in the griffon's head or in the pony's thoughts.
That said, overall a good, sexy read. I loved the bit with the drawing, and I'm a sucker for under-desk fun! Hope you keep this going!

Dead story?