Final answer:
The child with impetigo can return to school after 24 hours of starting antibiotic treatment.
Step-by-step explanation:
The accurate response to the mother's question about when her child with impetigo can return to school is after 24 hours of starting antibiotic treatment.
Impetigo is a highly contagious bacterial skin infection that is usually treated with topical or oral antibiotics. After 24 hours of starting antibiotic treatment, the child is no longer considered contagious and can return to school.
The other options mentioned, such as waiting for the rash to completely heal or for the scabs to fall off, are not the correct criteria for determining when the child can return to school.