I still think you need to buy the Evan Henry birth certificate.
Now is this John Henry's death?
John Henry Rees
Birth Date: 1 Jul 1901
Death Registration Month/Year: 1972
Registration district: Caerleon
Inferred County: Monmouthshire
Volume: 8c
Page: 387
Now I can see years being wrong on a death but a month to be July when the school record says September. I can't see that.
All I can think is that the school record, which will be a transcription from a primary scource is wrong. perhaps there were 2 John Rees and whoever wrote that record got them mixed up and put the birth date down wrong.
If that death is correct then he did live long enough to claim a retirement pension and like I said he would have to provide proof of his date of birth to do that.