The free ride could soon be over for many Gloucester, Mass., schoolchildren. The school district, seeking to make up for reduced state aid and sagging city revenues, has proposed a $250 annual bus fee for elementary school and middle school students. The fee would be charged kindergartners through eighth-graders who live less than two miles from their school and wants to ride the bus. Those in sixth grade or lower who travel longer distances are entitled to a free ride by state law.