The National Education Association is pouring $500,000 dollars into the campaign to defeat a State Amendment dealing with teacher tenure. According to the Missouri Ethics Commission the N.E.A. and its State affiliate are each contributing a quarter of a million dollars to defeat the measure which will be voted on next week. The contributions are in addition to more than one million dollars already given. If the Amendment passes, Missouri would become the first State to require a majority of teachers’ evaluation scores be based on student performance.