It appears that the article is looking at vaccination in addition to mask usage. There are many areas of the US where vaccination percentages are relatively low and vaccination percentage of children between the ages of 5 to 11 are even lower.
While children may not wear masks correctly, at a population level, it stands to reason that wearing masks will reduce the chance of transmission. Just like condoms have a theoretical effectiveness of 98% when used properly, but real world use shows an effectiveness rate of 82%, mask usage should still reduce transmission, but not to the extent that they would given proper use. But that doesn't mean that they're not effective at all and there's no need to use them. Looking at it from a population perspective versus an individual perspective in terms of transmission and the chance of contracting the disease, they should still have some beneficial effect.
The other part of the equation is the use of multiple strategies to mitigate transmission. For example, social distancing, limiting the number of people, and reducing the time spent indoors. All these factors put together will reduce transmission even if people aren't perfect in terms of compliance.
You may look at the data of how much protection masks add between the ages of 5 to 11 and 2 to 5. And how much other mitigations measures add (ventilation, cohorting, etc). You'll find that high quality masks for teachers reduce spread a lot. Masks for kids - the effect can't be clearly registered.
And using masks for kids, particularly outdoors is a hazard in itself. Masks tend to block lower peripheral vision. Which results in kids tripping and falling more often. Falls and playground injuries are a common cause of hospitalizations in the US [the order of 100k kids/year]. Masks also reduce ability to communicate [hazard]. And it is unclear what is the long-term impact on kids development.
Overall, at least to me, masking kids outdoors at this stage seem wrong. Indoor - questionable, it'd be good to see more statistics for this particular mitigation measure, if de-correlated from other mitigation measures.
> And it is unclear what is the long-term impact on kids development.
Keep in mind that it's also pretty unclear the long term effects of contracting COVID (even with no symptoms) in the first place. What about getting COVID twice? Three times? Four times? I'd rather do what I can to ensure my kids don't get it at all, are vaccinated, social distance, etc. Hopefully we'll get to a place where vaccinations / natural immunity reduce cases to a point where masks no longer make sense, but until then...
While children may not wear masks correctly, at a population level, it stands to reason that wearing masks will reduce the chance of transmission. Just like condoms have a theoretical effectiveness of 98% when used properly, but real world use shows an effectiveness rate of 82%, mask usage should still reduce transmission, but not to the extent that they would given proper use. But that doesn't mean that they're not effective at all and there's no need to use them. Looking at it from a population perspective versus an individual perspective in terms of transmission and the chance of contracting the disease, they should still have some beneficial effect.
The other part of the equation is the use of multiple strategies to mitigate transmission. For example, social distancing, limiting the number of people, and reducing the time spent indoors. All these factors put together will reduce transmission even if people aren't perfect in terms of compliance.