Children with strep throat should not be excluded from school. if they have no fever or feeling well.
There is no evidence that keeping children at with strep throat do reduce spread of infection since there many children (10 to 15%) who carry strep in their throat who do not have symptoms.
Also the risk of transmission is less than 10% only. The period of infectiousness is not known while the
duration of shedding of strep is from 1 to 12 months if untreated, and if treated, four days.
Reference - Pediatr Infect Dis J 2001 Apr;20(4):380, Pediatr Infect Dis J 2001 Jul;20(7):653,Pediatr Infect Dis J 2001 Dec;20(12):1184