You need to load an earlier save so you have time to get your Childs grades up. In the future make sure to keep the grades above F. Once you child has had an F for a couple days it will be taken away. If you make sure they do their homework every other day they will retain the D they start out with. Doing homework every day makes sure that grades will increase. Doing the tasks on Mondays will increase grades even faster as will doing extra work and working hard in school. The latter will make them stressed so only use if absolutely necessary.
