Australian cops apologized yesterday after inadvertently sending kiddie porn to 1,800 schools while trying to warn principals about children at risk of abuse.  The mistake came during a police crackdown on child pornography that so far has resulted in more than 200 arrests, including police, teachers, clergy and the owner of a child care center, after more than 400 raids.  The images the principals were to see were only of the girls' faces; but the cropping somehow vanished when the recipients opened the mail.