A former teacher from Tennessee entered a plea of guilty yesterday to crossing state lines to have sex with a 15-year-old student. Fifty-one-year-old Tad Cummins also pleaded guilty to obstruction of justice in federal court in Nashville. Cummins faces a mandatory minimum of 10 years in prison for crossing state lines for sex with a minor. He also faces up to 20 years for obstruction of justice for destroying his and his former student’s cellphones when he fled with her. He will be sentenced later this year. Cummins disappeared with the girl last March. They were found in April at a remote forest cabin near Cecilville, California, after a tip to police.