suitably resourced campaign to back it up
This is important. Current funding in a London Borough that I worked in covered about 1/3 of the school children there for quiet roads. Virtually no funding for the advanced course on busy roads e.g. specifically covering not passing vehicles on the inside. Since it causes so many casualties, it’s something I always try to mention, but it’s not on the syllabus so if you are short of time or have badly behaved kids, it might not make it in there.
And the award of council contracts is a race-to-the-bottom on funding, driving anyone who has any sense to get out of being an instructor and do something where you can make a living.
Personally, I think it would be great to put all children on the course in Primary, and then again (for the advanced stuff) in Secondary.
Even with the modest resources we had, though, many parents didn’t want their children to take part. Either because they didn’t want them out of lessons, or they didn’t want to make the bike roadworthy (even though we would fix them), or maybe they just thought the whole thing was pointless.