South Carolina ? A Chesterfield teenager accused of plotting to bomb his high school is a straight-A student whose parents sought help from mental health experts when he slammed his head into a wall last week, authorities said Monday.

Ryan Schallenberger’s parents took him to a hospital three days before his Saturday arrest after he made a 4-inch indentation in the wallboard, prosecutor Jay Hodge said at a court hearing.

Schallenberger, 18, was not badly injured, but his parents also called a local mental health clinic that offered no help, Hodge said. A spokesman for the clinic would not confirm or deny any contact with the family, citing state law.

Hodge said he plans to ask that Schallenberger undergo a mental evaluation at the teenager’s bail hearing today.

Schallenberger was arrested after his parents called police because he had ordered 10 pounds of ammonium nitrate, an explosive commonly used as fertilizer and was employed in the deadly 1995 Oklahoma City bombing.

Authorities checked the school for bombs over the weekend and on Monday students walked through newly installed metal detectors and past law officers. Still, officials said 60 percent of the school’s 544 students stayed home.