Fifth-grade teacher Melissa Carpenter works a 10-hour day on average during the week, and her job sometimes requires her to put in hours on weekends, too. “I feel like teaching is one of those jobs where we go to work to do more work — to do work after work,” said Carpenter, who teaches at William B. Wade Elementary School in Waldorf, in Charles County. Carpenter’s long hours are far from unique among Maryland’s educators, as the state and nation grapple with a teacher shortage.