Brian Wonsom, 15, pleaded guilty today in Prince George's County Circuit Court. Wonsom, who was 14 at the time of the killing but faced adult charges, was sentenced to 85 years in prison.
Defendants convicted of violent crimes in Maryland are eligible for parole after serving half their sentence.
In pleading guilty, Wonsom acknowledged killing Hannah Wheeling, who was found dead in February 2010 outside a cottage at the Cheltenham Youth Facility in Prince George's County.
The 65-year-old English teacher was from Bel Air, Md. She was reportedly last seen alive giving a test to Wonsom.