You shouldn't try to get out of going to school.
Barbara told her mom about a mild stomach ache and Barbara's mom asks her if she wants to go to school.
Barbara wants to tell her mom what she will do.
Barbara tells her mom she can go to school because the stomach ache isn't bad.
Barbara tells her mom she won't be going to school because of the stomach ache.
Barbara will be able to learn the lessons of the day.
Barbara will miss out on the lessons for the day and fall behind.