Continuity mistake: After all the actors have left Fran and Maxwell start to leave the room Fran is holding a clipboard by the side, in the middle. When they go into the hallway she is now holding it by the bottom.
Continuity mistake: In the kitchen at the beginning when they are sitting at the table Fran says "Gracie when do you come up with these things." There is a note pad with a pencil on it in front of Grace. The shot changes and Fran is holding the pencil - the next shot Grace is now holding it.
Sunday in the Park with Fran - S1-E18
Continuity mistake: When Fran is sitting at the table with Grace when C.C. is on the phone, the coloring book in front of Grace is open. Fran goes to pick it up, the shot changes, and Fran has already picked it up.
Sunday in the Park with Fran - S1-E18
Continuity mistake: When C.C. is trying to get Grace to play with the son of the Broadway critic she is coloring with a green crayon. Near the end of the scene it is suddenly a red one, and the paper she is coloring on is all red with no green so she could not have changed colors.
Answer: Mr. Sheffield needed someone to manage the kids, not necessarily babysit them. Brighton was a Bart Simpson type, Maggie was shy and awkward and Gracie had personality issues.