Students across the Bay State could have longer school days, a shorter April vacation or even class on Saturdays as districts grapple with an academic year extending well into the hot days of June.The predicament has angered many Boston parents and teachers in schools without air conditioning.After superintendents canceled school for what turned out to be only a dusting of snow in much of the region yesterday, district representatives now must contemplate several ideas to spare kids from roasting in classrooms in late June.