As his days as Fairfax County schools deputy superintendent come to an end, Richard Moniuszko has been preparing to head back to the classroom as an associate education professor at George Mason University.

Moniuszko, who joined Fairfax in May 2006, helped oversee the daily operation of Virginia’s largest school system, with 184,500 students, as the “back-up quarterback” to Jack D. Dale, who retired in July. Moniuszko will step down after the first of the year.

“It’s a hard place to leave because of the people,” Moniuszko, 63, said. “Some of the best educators in the country work in Fairfax County.”

Moniuszko, a Baltimore native and graduate of the University of Virginia, served in administrative positions in North Carolina and South Carolina before answering an advertisement for a job in Fairfax.

“I was familiar with Fairfax as a premier school system,” Moniuszko said. He later sat down with Dale for an interview, and they connected on philosophical issues related to addressing minority student education.

“I asked him, ‘When are you making a decision?’ And he said, ‘I just did,’ ” Moniuszko said.

Moniuszko oversaw teacher development and student learning in Fairfax, with a particular focus on closing the achievement gap and graduation rates.

“We’re making good gains,” he said. “It’s tough work, particularly with high-poverty students. But I think we made a difference.”

Moniuszko acknowledged that the county’s black and Hispanic students continue to lag behind their white and Asian counterparts by double digits on standardized tests. In Virginia, test score benchmarks were changed in recent years, which led to a significant widening of the difference between the student groups.

“It’s like a high jump,” Moniuszko said. “When you reach the bar, they raise it again.”

Moniuszko said that as he leaves office, he regrets that the school system does not have more reliable funding for construction projects. He said that schools wait years for renovation, and that many facilities are crumbling as the county faces budget constraints.

“We’ve been in survival mode,” Moniuszko said. “I’d hate to reach that tipping point where achievement starts to decline. It’s really hard to climb out if that happens.”

Former Fairfax assistant superintendent Dan Parris will replace Moniuszko in the interim until new schools chief Karen Garza names a permanent successor.

Beginning Jan. 13, Moniuszko will teach three classes to graduate students and doctoral candidates on the art of school administration. Moniuszko said Fairfax teachers and principals will fill his classes at George Mason, where he will help train the next generation of the school system’s leaders.