DELAND, Fla. — A Florida boy accused of killing his mother during a fight over a bad grade pleaded not guilty to a first-degree premeditated murder charge Thursday morning.

Gregory Ramos of DeBary also pleaded not guilty to the two other charges he faces — tampering with a crime scene and abuse of a dead body — during a hearing at the Volusia County Courthouse.

The teenager is being tried as an adult in the death of 46-year-old Gail Cleavenger at their home November 1.

According to an arrest report, investigators say he strangled his mother during an argument over a "D" grade he got in class. They think he used a wheelbarrow to load her into a van, then buried her body under a fire pit at a church. Deputies have also charged two 17-year-old friends in the death, who they say helped Ramos, with accessory after the fact of first-degree murder.

Because Ramos is younger than 18, he won't face the death penalty, the State Attorney's Office said.

Ramos' next court appearance is a pretrial hearing set for 8:30 a.m. January 23.