J.H.
If your son has just strep, he could return to school after 24 hours of antibiotics. Since he also has Influenza A he definitely needs to stay out of school until it's been 24 hours without a fever and he's showing decreased signs of a cold (which unfortunately can be up to a week). Infuenza A is highly contagious and can be life-threatening to some kids (not to scare you).