Final answer:
Leonard's parents should insist he returns to school and teach him coping skills, understand the root of his fear, and reinforce his self-confidence and competence.
Step-by-step explanation:
To assist Leonard, who is 11 years old and suddenly afraid to go to school, his parents can best help by firmly insisting that he return to school while training him in how to cope with difficult situations. This approach avoids reinforcing the fear through avoidance and instead empowers Leonard with the skills necessary to face and overcome his fears. Being protective or allowing him to avoid school could actually worsen the anxiety in the long term. Instead, his parents should engage in open conversations to understand the root cause of his fear and seek professional help if necessary. In addition, they can support positive social activities, praise his efforts at school, and help build his self-confidence and sense of competence, which is crucial according to social development stages.