Britain's Education Secretary Damian Hinds says it is a scandal that some children still start school unable to speak in full sentences or read simple words. Children who start school behind their peers rarely catch up - the gap just widens, Hinds will say in a speech pledging halve the number of pupils starting school behind in early talking and reading skills by 2028.
A group of companies and charities have been brought together to work out how best to support families in England.
Educational researchers have long said that social mobility - or the lack of it - starts at home with what's known as the home learning environment.
The idea is that a home with a lot of books and other early learning materials, plus engaged parents giving their children quality time, talking with them and teaching them how to make letter sounds, for example, provides a good start.
But not all parents feel able to offer this kind of home environment or realise the importance of it.
Researchers from the Education Policy Institute last week said the development gap between England's poorest pupils, and the others, was already at 4.3 months in the early years. And that it grew to 9.4 months by the end of primary school.
Hinds will say, in the speech in London, that this early gap has a huge impact on social mobility.
The truth is the vast majority of these children's time is at home. Yes the home learning environment can be, understandably, the last taboo in education policy - but we can't afford to ignore it when it comes social mobility.
I don't have interest in lecturing parents here... I know it's parents who bring up their children, who love them. who invest in them in so many ways, who want the best for their children.
But that doesn't mean extra support and advice can't be helpful.
The Department for Education says 28% of children in England do not have the required language skills by the end of Reception. But this rises to much higher percentages in deprived areas.