Although many experts reccommend only local therapy without a culture, what bacteria (staph strep, or both) and what antibiotic to use can't be known without a culture. Also, the child or others may have the bacteria in their respiratory tract and give it to others. So I reccommend oral therapy with the approriate antibiotic. The child can return to school ofter 24 -48 hours of antibiotic.
No. Though many experts reccommend only local treatement, without culture, our studies in families show that a culture is needed to see if impetigo is staph, strep or both, and what antibiotic it is sensitive to. Also, since there may be infection in the respiratory tract that is infectious to others, local treatment will not prevent spread, without appropriate oral antibiotics.
No. You should keep your son out of school until the lesions stop oozing and crusting. This should happen before he is finished with his medication.