High school English instructor Erin Cougill has failed the mathematics part of the state's teacher certification test six times. If she does so again, she'll lose her job. The Central High School teacher, who also is secretary-treasurer of the Hernando Classroom Teachers Association, plans to take the test again May 13. If she doesn't pass, her job will become open June 1. Cougill, 36, acknowledges she has a "math block.'' Some of her students recently spoke out on her behalf, submitting a petition attesting to her abilities and criticizing a state law requiring teachers to pass a general knowledge test...