The disease control committee said it had tested 72 teachers and 1,202 students using the antigen test kits, and 90 tested positive. They were isolated at the Wat Phudantae field hospital and tested again using the RT-PCR method, which came up negative.
Parent Taweesak Nareenuch, 45, said he was glad his daughter had tested negative and that he could take her home.
Parents, teachers and students have been advised to monitor symptoms and inform public health officials if they develop a fever, phlegmy cough, sore throat or have trouble breathing.