Kathy Sylva, a professor at Oxford University, told the annual conference of educational psychologists in Scotland that middle-class parents often gave their children coaching that others could not.
"In the UK, we have the world's most proactive middle-class parents when it comes to helping children's development," she said.
But she added that children from working-class backgrounds often fell behind without the early boost of museum trips and home computers. "It is not just providing the setting; it is helping the parents to provide it at home."
Professor Sylva suggested clapping out syllables with infants to prepare them for learning to read. "There are many things in the playground which can really help children make a start on the curriculum."
Trained staff in nurseries also boost infants' learning, she said.
"Qualified teaching status makes a big difference in behaviour and education outcomes," Professor Sylva said.
As an example, she showed delegates a conversation between nursery children and their teacher. Some had trainers which lit up when they walked, sparking a discussion about why.
When the teacher pointed out that her trainers were new but didn't light up, one of the youngsters suggested the shoes had batteries in them.
Professor Sylva described this as an example of the best teaching, as it led the child to think for himself: "It is more likely we will have a conversation of this pedagogical quality if we have a trained teacher."