Some really interesting thoughts.
Certainly the commonly-held belief that teenagers - and especially girls going through puberty - are central to the phenomenon ignores some well documented cases in which that factor was absent (the South Wales mower repair shop case for example) and as mentioned above, UFO cases.
The Battersea poltergeist [
https://www.historyextra.com/period...anormal-cold-cases-the-battersea-poltergeist/] did involve a teenage girl and this polt did allegedly follow her to school and a tv studio, although the great majority of activity happened within the house. But then like some other cases the whole affair started to tie itself in knots with frankly unbelievable reported levels of activity (and yet not a single photograph) and then some rather convoluted story about a young French prince.
Likewise, the Enfield poltergeist had a strong start but then also became a bit of a pantomime in the end, with the girl grinning for the camera as she 'manifested' the dead man's voice. Also, there were four children, so what were the other two doing whist Janet and Margaret were downstairs with mum and the investigators? Perhaps hiding out of sight at the top of the the stairs and throwing down objects? These other two children are rarely mentioned but their very existence opens up the possibility of childish hoaxing. Moreover the evidence from the people in the street who claim that one of the girls was levitating has to take into account the limited view and the fact there were three other children who might have been involved (for example, you can lift someone up horizontally by lying on your back, putting both feet in the small of their back and using the strength of your legs).
Both cases were also investigated by people who wanted to believe in life after death and so inherently biased. Also, I've read some pretty thin excuses for why Grosse and co didn't have film cameras with them in the late-1970s, even some grainy cine film of the activity would have bolstered the case immensely. However, both cases were quite convincing in the earlier stages