Striking teachers in Portland, Oregon, temporarily shut down a major bridge Tuesday morning as they marched across it. KGW reported that the Portland Association of Teachers union and their supporters stopped in the middle of the Burnside Bridge for about 15 minutes. The union posted photos on its Facebook page showing teachers sitting down on the bridge. According to KGW, by 9 a.m. the bridge was clear and cars were driving across. Portland teachers have been on strike since Nov. 1. Class sizes and teacher salaries are among the key issues the union and the school district have been negotiating.