[tokenadult]

just delay going to school until age of 7

Delaying the start of formal school attendance (which my family achieves up to the age of fourteen or so by homeschooling) is very helpful indeed, but it is not a complete preventive measure for attention problems. I know lots of homeschooled children who have plenty of attention-regulation difficulties, and on the other hand I know children who have attended school since preschool age who do just fine in focusing their attention. (I am a teacher and regularly meet young people in my math classes who began school attendance early.)

In most of these matters, family history makes a big difference.[1] Sure enough, the children I know who have the most trouble regulating their attention have parents who have difficulties with the same issue, although perhaps not so severe by adult age. The suggestion of the press release you kindly shared that not going to school as soon as is typical recently is a good idea is an idea that is plausible to me, but it will not entirely prevent ADHD.

[1] http://www.cdc.gov/genomics/famhistory/

http://www.healthline.com/health/adhd/genetic#Causes2