Evidence suggests there was no benefit to Ontario closing its schools
“By comparing the experience of Ontario with that of other provinces it is now clear that provinces that kept schools open longer had outcomes that were no worse and, in many cases, better. The timing of the spring wave, in particular, was remarkably similar across B.C., Quebec and Ontario, with peaks occurring on almost the same day across all three.
Yet, the first two kept schools open throughout, while the last closed them in April and never reopened. Evidence from across North America now suggests that the damage caused by closing schools was inflicted for no benefit.”