A Maryland teenager calmly admitted in court Monday that he beat his mother to death with a baseball bat after an argument over his grades at a prestigious private school.

Lewin C. Powell III, 16, wore a dark suit and showed no emotion as he answered questions from Baltimore County Circuit Judge Kathleen G. Cox about whether he understood the significance of his guilty plea to first-degree murder.

Prosecutors are seeking a life sentence with the possibility of parole when he is sentenced April 3. Powell's attorneys plan to ask for all but 15 years of the sentence to be suspended and to have their client sent to the Patuxent Institute, a maximum-security psychiatric facility with a program for young offenders.

Powell did not stir when a prosecutor read a statement of facts that detailed the prolonged attack on his mother and a similar beating of his father, who survived.

"He's always taken responsibility for what he's done," Shanell Kathleen Harleston, one of Powell's attorneys, said after the hearing. "He never wanted to prolong it."

Powell killed his mother, Donna R. Campbell-Powell, in May after an argument about his grades at McDonogh School, a prestigious private school in Owings Mill where he was a sophomore. But Harleston said the initial subject of the dispute with his mother was immaterial.

"This is a lifetime of problems that he's been dealing with that suddenly came to a head," Harleston said. "This particular day was the first time he had ever argued back. ... He just snapped that day."

Harleston would not specify what led to Powell's emotional difficulties, but the teen told police after he was arrested that his parents had pushed him too hard and he couldn't take it anymore, according to a statement of facts read in court Monday by Assistant State's Attorney Charles R. Gayle.

Harleston said Powell was not abused by his parents.

In exchange for Powell's guilty plea, prosecutors dropped all other charges, including a count of attempted murder for the attack on his father, who suffered two skull fractures when his son beat him with the same aluminum bat.

State's Attorney Scott D. Shellenberger said after the hearing that he did not believe Patuxent was an appropriate placement for Powell. Prosecutors will argue that Powell should serve his sentence in a state prison.

If he receives a life sentence, Powell could be eligible for parole after 12 years with good behavior. Parole for an offender serving a life sentence in Maryland requires the approval of the governor, which hasn't happened since 1994.

The son of Jamaican immigrants, Powell lived with his parents in an upper-middle-class neighborhood in the Baltimore suburb of Towson. He had no history of violent behavior and took honors-level classes at McDonogh, where annual tuition exceeds $20,000.

Powell's father, Lewin C. Powell Jr., arrived at the hearing about 15 minutes after it began. As Gayle read the statement of facts, the elder Powell buried his head in his hands. He declined to speak to reporters after the hearing.

Harleston said she planned to call about a half-dozen witnesses to testify on the son's behalf at his sentencing. Prosecutors intend to call Powell's father, but Harleston said the elder Powell does not wish to testify against his son.

According to the statement of facts, Powell's mother picked him up from his school bus stop on the afternoon of May 13 and told him she had received a call from McDonogh about his academic performance. The two began to argue and, after they got home, Powell began punching his mother.

At one point, she tried to run outside, but he stopped her at the front door and punched her again repeatedly until she was in what he described as a "daze." He then decided to kill her and moved her near a back door, then grabbed his baseball bat. When he started hitting her with the bat, she was reaching up in an attempt to get out the back door.

Powell then hid his mother's body in a garage and cleaned the house. His father got home late that night and went to sleep on a sofa. Early the next morning, Powell began beating his father in the head with the bat. The elder Powell talked his son out of killing him and told him he would withdraw money from his bank account to help the boy escape.

In the meantime, two of Campbell-Powell's co-workers came to the house to check on her and called 911 when no one answered the door. When police arrived, Powell and his father were in the back yard.

"Thank God you're here," the elder Powell told police. "My son killed my wife."