My child went to urgent care yesterday to get treatment for her strep. they said she should be ok to go to school today. i thought she was contagious for a full 24hrs.

At least 24 hours: You are correct. The aap red book, our infectious disease reference, indicates at least 24 hours after starting antibiotics before school or daycare attendance. I would add that the child should be clinically well and without fever.

Strep Pharyngitis: Spreads very fast among children from saliva/close contact. Better to keep her home at least 24-48 hours after starting treatment. Penicillin group of antibiotics cures 99+ %.

Wait: Because strep is contagious for 24-48 hours after antibiotics start, you should wait before sending your child back to school.