The city fired or demoted 45 principals for "poor performance" yesterday, but critics blasted the move that they said also targeted good veterans. Over the past few weeks, the targeted principals were faxed a 10-point agreement that required them to keep quiet about terms of departures and demotions in turn for avoiding "unsatisfactory" ratings. If they signed the agreements, they could return as consultants, the sources said. In some cases, they were given only a few hours to make a decision. "They took my life from me," said one Brooklyn principal, who got news of his academic performance bonus, then...