Ask your child why she doesn't want to go to school. Make sure you ask during a time that you can devote your attention to her answer, so that she feels you value what she has to say.
Troubleshoot ways to help him solve the problem. For example, if other kids pick on him, encourage him to tell his teacher. If you have an older child who is being picked on, tell him to avoid associating with bullies and ignore their behavior. If he complains that school seems too hard or too boring, make an appointment to talk with the teacher. If he complains of loneliness, find a way to get him involved in some extracurricular activities or allow him to invite someone he'd like to have as a friend over to your house. If he doesn't like his teacher, schedule a conference with the teacher to determine what that is all about. You may decide to request a transfer for your child if the personality clash can't be resolved.
Ask your child about experiences at school. Find ways to connect what she learns at school to her past or future experiences. Enrich what she learns at school. For example, if your child learns about the solar system at school, do some star gazing at night and talk about constellations and planets. This can help make learning more meaningful for her and help her appreciate school more.
Reassure your child during bouts of anxiety or nervousness over testing or other academic challenges he may face. Spend time talking about working through his feelings and using them to his advantage.