The Shezen contact study found the same risk of infection for children as for adults(https://www.medrxiv.org/content/10.1101/2020.03.03.20028423v...).
According to the results of Fundan University, school closures led to a 40%-60% reduction in new infections (https://science.sciencemag.org/content/early/2020/04/28/scie...).