Washington (AP) - It took a while for the class to warm up to him, but Marion Barry quickly had about 15 Ballou High School students talking chemistry.

The four term ex-mayor and current Ward 8 councilman returned to his teaching roots on Thursday. At a school in one of the District of Columbia's roughest neighborhoods, Barry taught a lesson on conducting electric current. He called on sleepy-eyed students, pressing them for answers about solutes and solvents that form various solutions.

He also offered the students some life lessons.

"One thing you've always got to do is speak up," Barry told the class. He said young people should always take their education and their relationships seriously.

"Be careful of the people that you step on the way up," he said, "because sometime you'll meet them on the way down."

Besides talking chemistry, Barry, 68, told students not to butcher the English language and not to smoke. He even broached the topic of sex.

"I'm old fashioned. I believe in abstinence," he said.

Miyonna Bennett, 15, said students respect Barry "as a black person who's accomplished a lot." Jerrell Grooms, 17, didn't care that the former mayor had spent time in prison for a drug conviction.

"Nobody's perfect," Grooms said. "At least he's back now. He came back to help the community."

Barry took his council seat this month, six years after leaving the mayor's office. He said "improving this raggedy school system" is at the top of his agenda. School Superintendent Clifford Janey said Barry was raising the standard for other city leaders to support the schools.

Janey also spent Thursday at Ballou, serving as "Principal for the Day." Janey met with student government leaders who told him relations with their principal, improving security and better lunches were their top complaints. They said poor bathroom facilities were affecting students' well-being.

"We need to get this wrong righted," Janey told the students, promising he would return with his staff to talk about improvements.

"I do value the views and opinions of our students," Janey said. "It means a lot for us to be able to see the world - not through the eyes of adults, but through their eyes, unfiltered."