The Mesa (Ariz.) Community College transfer left this week, a team spokesman confirmed to the Journal Star on Tuesday morning.
Jackson, a 6-foot-3, 200-pound corner arrived on campus in June and expected to compete for a starting job in a relatively thin position group, but didn't make the progress up the depth chart he expected.
Secondary coach Travis Fisher on Monday said Jackson had been slower than some of the others to learn the playbook.
"We appreciate the competition Will helped incorporate into the room and we wish him the best," the school spokesman said.
Fisher is not one to mince words, and he made it clear Monday why Jackson had not locked down a regular role.