If they were low enough, the 2x rise might not be very statistically significant either.
UK Covid hospital admissions for 0-5, using a 7 day average, peaked at 12. It progressed gradually since October and is now over 20.
6-17 age group peaked at 12, progressed gradually since October and is now around 15.
The data set is huge and the numbers are most definitely significant.
https://twitter.com/Datagraver/status/1345858984750821381/photo/1Israel currently has 50,799 known active Covid infections. 10,381 of them are school students. That's with many schools closed in 'red' areas.