For the vast majority of children and parents it has no impact whatsoever, health visitors and teachers in promoted positions already have a duty of care to pass on any serious concerns.
What it does change is that for pre -school children, there is now the expectation that they will see a health visitor at least at some point. A few years ago lots of areas stopped doing routine checks and developmental checks for parents that weren't in an 'at risk' group, I have huge issues with that, partly because there's the assumption there that abuse and neglect only happen in certain types of families, but also the assumption that other types of parents will recognise and know how to access support for developmental delays or disabilities, the onus should not be on parents to seek help for something like that.
In secondary schools (an area I have experience in) it's very easy for children with issues to go unnoticed if they don't speak up voluntarily, in a class of 30ish pupils it's very hard to tell if a pupil at the back of the class saying nothing is fine and just a bit of a quiet person or if they're quiet because there are huge issues outside of school. Now, someone has to be checking in with them and it raises the possibility that it won't go unnoticed because nobody had time to check.
I also think that agencies involved with children absolutely should be sharing information and it's ludicrous that despite lots of other initiatives that are designed to do just that, you can still have seperate agencies all involved with one child all receiving different information and not passing on relevant things.
Basically it's designed to flag up the children that are currently missed, the ones where a family put on a good front but there are horrible things happening behind the scene, the ones that have other agency involvement but everyone is passing the buck a bit and the ones with low level stuff going on that wouldn't otherwise be noticed. The cases you read about in newspapers where despite social services involvement and massive concerns at school nobody actually sees the child until they're dead, or the ones where there are lots of little flags being raised all over the place but nobody is doing anything because they're kept as seperate files at seperate agencies.
I know there's supposedly issues with the way the it's been written - I wouldn't know as I'm not a legal expert.
I also know that it's criticised for being easy to misuse if someone dislikes a parent or is vindictive... But, if health visitors or promoted teachers are behaving like that then they could do quite a lot with the systems that were already in place.
What it definitely does is make the named person accountable for actually checking that a child is ok, rather than how it was where it was part of their job, but in a vague way and no real consequences if they missed some because there were no pressing concerns.
My that was long, lol.