Twoin- with all due respect, you are only seeing one piece of the puzzle on your neighbors. You may not realize that the girls have significant medical or neurological needs- such that the level of functioning you see is miraculous given their challenges. These may have been the kids we read about who get bounced from school to school when the administration can’t figure out how to comply with the law… and it’s too costly to actually try and address their issues. I have a sibling who teaches special needs kids in a private school and the stories she tells about 9 and 10 year old kids who have been in five and six schools- none of which were willing or able to provide what their IEP required- it’s really sad.
So sure- decide that they’d have been better off in public school. Maybe what you are seeing is an absolute success story- kids who would have been marginalized in a classroom who can now hold an adult conversation, pursue their own interests (not everyone wants to join a sports team) and realize their own potential.
There are lots of people in the world who “miss being kids”. Sometimes it’s due to illness or disability, or a siblings illness or disability. Sometimes it’s because a parent is neglectful or narcissistic. Your neighbors sound like a mighty success story to me- many of the people in society who didn’t get to be kids are in jail or are making crystal meth in mom’s garage.