Good luck on your hunt!
I remember when I was in high school, a friend and I had a plan to go on a spring bear hunt in Montana. We had it approved through the school, and as an approved absense. We each had to write an essay, do a certain amount of research regarding black bears, and a couple other little things, but nothing major really. Unfortunately, we did not get to go on that hunt, as we were broke high school kids. But we sure had the OK from the school.
That was only 8 years ago, so I guess the moral of the story is, keep your grades up, and be willing to compromise with the school administration (not the teachers, they have no say in whether the absense is excused or not), then you are good to go. It may sound like a long shot, but you know how that saying goes.
Later,
Marcial