North Wasco County School District 21 may not be able to issue zone waivers for elementary schools next year.  D-21 Superintendent Candy Armstrong says growing capacity issues have gotten to the point where they may no longer be able to accommodate requests from parents to allow their children to attend schools outside of their neighborhood.  She adds the problem could be exacerbated by the establishment of farm worker housing in the Colonel Wright attendance area, where space is already limited.  Armstrong estimates over 100 D-21 elementary students currently receive zone waivers.  Elementary school principals are currently studying the issue, and the district will make a decision sometime in May.