 When the union's collective bargaining agreement expired in June 2006, the OPSB declined to renegotiate the agreement.As of late December 2006, only 27,066 of New Orleans' pre-Katrina student population of 66,372 had returned.Only 54 schools were open, with 20 of these operated by OPSB, charter schools approved by OPSB or charter schools approved by the state board of education.