Rehiring the teachers could cost the city as much as $7.5 million,
The teachers were dismissed in 2008 by schools Chancellor Michelle A. Rhee, The Washington Post reported Thursday.
About 1,000 educators were terminated during Rhee's 3 1/2 years as chancellor.
Arbitrator Charles Feigenbaum argued the dismissals were unjust because the teachers, who were in their two-year probationary period, were not told why they were fired.
The dismissals came before the 2009 launch of IMPACT, an evaluation system for teachers that calls for dismissal or a grace period for those with poor ratings.
The district argued that Feigenbaum acted outside of his authority and that the school system had the right to fire the teachers during their probation period because they got negative assessments from their principals.
The board said in its Sept. 15 decision that Feigenbaum acted appropriately when he reinstated the teachers in February.
Schools spokesman Hassan Charles said Thursday the school system's attorneys are discussing whether to appeal the case.
"It is time to stop stalling and put good teachers back to work with deserving students and parents," said Washington Teachers' Union President Nathan Saunders.