Child with strep, confirmed by rapid test, has been on antibiotics for 4 days and still has fever?

Unusual: If it was clear the diagnosis was strep and he/she are on the correct antibiotic and dose and there were no complications, he/she should be better by 4 days or sooner. I would have a recheck to see if anything should be changed. All the best.

Other issue: Kids can often test positive for strep when the also have a throat virus. Co-infection is common. If the kid is not better I'd call today. If the med is from the penicillin family it will kill the strep but not a virus.