BUTTONWILLOW, Calif. (AP) - Kern County authorities arrested a teacher today on charges that she had a sexual relationship with one of her 12-year-old students. Authorities say Sherry Brians, a 41-year-old teacher at Buttonwillow School, had been under investigation since before Christmas. The 12-year-old boy's mother went to authorities after finding a letter in her son's backpack that indicated the two had a romantic and physical relationship at the school.