CARSON CITY, Nev. (AP) - A national educational testing company criticized for mistakes in grading proficiency exams of more than 700 Nevada high school students has been given an $18 million extension on its contracts. The state Board of Examiners, chaired by Gov. Kenny Guinn, voted Tuesday to approve contracts for Harcourt Educational Measurement to continue developing and grading tests for Nevada's elementary and high school students. The Harcourt contracts are with the state Board of Education, which levied a $425,000 fine against the company that mistakenly informed 736 high school sophomores and juniors they had failed the high school...