However, if these results were observed in grades 3 or higher, it could suggest a more substantial phenomenon. I randomly picked the third grade, but perhaps there’s a specific age after which the medical community considers a child’s immunity to be significantly enhanced.
I exaggerate a bit, but I found that during covid, where the mask was mandatory in my place, I was never sick. The only few years in my life where I was actually healthy continuously for YEARS, I and my friends could not believe the impact of the mask. But then we were stuck at home, living in constant misery and stress.
Once the masks disappeared, finally we could live again, and got extremely sick the first few years... Maybe a more normal balance would have been better ? Sick a bit continuously ? I think trying to avoid sickness is like trying to swim against the current, nature just works that way.
A good overview of the allergy situation is here: https://en.wikipedia.org/wiki/Hygiene_hypothesis
Though that article goes into more about young human immune systems too. TLDR: Yeah ... it's complicated, but the evidence seems to, just maybe, lean towards more exposure being better. So, you're right, I think?