What disappointing news does Catherine find out from her next door neighbors in the book rules by Catherine lord?

In "Rules" by Cynthia Lord, Catherine learns from her next-door neighbors that they are moving away. This news is disappointing for Catherine because she has formed a close friendship with their son, Jason, who has cerebral palsy and relies on her for support and companionship. The impending move signifies a loss of connection and stability in her life, highlighting her struggles with change and the challenges of maintaining friendships.