Kevin Ricks, the former Manassas high school teacher who admitted abusing numerous teenage boys over his lengthy career, entered a guilty plea to a second-degree sex offense in Maryland on Friday.

Ricks, 52, agreed to accept responsibility for abusing a German foreign-exchange student who lived with Ricks in Federalsburg, Md., during the 2003-04 school year. Authorities had said Ricks got the student drunk, to the point of passing out, and then sexually abused him.

The student told The Washington Post that he was unaware of the specific abuse but left Ricks’s home and fled to another host family after feeling strange about the situation.

Ricks, who previously admitted in federal court in Virginia that he staged naked photographs of boys he abused while they were passed out, is serving a 25-year sentence . With the new conviction, he could face a maximum of an additional 20 years in prison.

The Caroline County case is the most serious sex offense for which Ricks was charged.

“This portrays, for once, what he actually did,” Caroline County State’s Attorney Jonathan Newell said. “He was entrusted with this boy’s care and should have been vigilant in protecting him. Instead, he spent an entire year scheming to have his way with him.”

A Washington Post investigation published in 2010 discovered that Ricks had abused boys in Virginia, Maryland, North Carolina and Japan.