(Providence, RI) -- Bus drivers for Providence Public Schools students are set to strike, possibly as soon as Monday, after contract negotiations reached an impasse yesterday. School bus company First Student said in a statement that it is extremely disappointed that union leadership chose to walk out of a federally-mediated session instead of negotiating in good faith. The contract dispute centers around bus drivers wanting to earn a pension instead of a 401-K plan. About nine-thousand students and their families would be impacted by the strike, which union officials say will not start on Friday.