By RODNEY MUHUMUZA BUSIA, Uganda (AP) — Dressed in his school uniform, Mathias Okwako jumped into the mud and started his daily search for gold, a commodity that may be closer to his grasp than another precious asset: an education. His rural school in Uganda sits idle just across the road from the swamp where he and scores of children now work as informal miners. Weeds grow in some classrooms, where