By YURI KAGEYAMAKUMAGAYA, Japan (AP) — The humble blackboard is serving as the canvas, and colorful chalk the paint, for young Japanese artists. “Kokuban Art Koshien ” is an annual national chalk art championship for high school students. (AP Photo/Hiro Komae) ExpandThe use of blackboards for creating artworks existed before in the Japanese school system. It was a stunning replica of Da Vinci’s “Last Supper” by an unknown artist on a school blackboard that caught Nichigaku’s eye. “Back then, there was graffiti, but there was no genre called blackboard art,” said Nichigaku President Tomohiro Yoshida.