P211 CEEFAX 211 Tue 19 Jun 21:11/41       A teachers' union has accused Education Secretary Sir Keith Joseph of trying to prejudice the decision of possible arbitrators in the teaching pay dispute The attack follows a Commons statement bz Sir Keith, in which hj said no more money was available even if the dispute went to arbitration. NU$ general secretary Mr Doug McAvoy said hj was trying to nobble arbitrators even before their work had started. Sir Keith said the teachers' action was causing immjnsj damage to school- children.