The government is enhancing Sure Start children's centres in the most disadvantaged parts of England, as research shows they benefit toddlers.
An earlier evaluation had shown less positive effects
A study by Birkbeck, University of London found children behaved better and more independent under Sure Start.
Their parents provided a better home learning environment than in areas without such Sure Start centres.
The positive effects were modest, researchers said. Ministers are funding more outreach workers and training.
Sure Start has local flexibility, but in general, services include outreach and home visiting, family support and good quality play, learning and childcare facilities.
The study, The Impact of Sure Start Local Programmes on Three Year Olds and Their Families was carried out by the National Evaluation of Sure Start Research Team at Birkbeck, University of London.
It focused on more than 9,000 three-year-olds and their families in 150 areas who initially had been studied when the children were nine months old.
These were compared with 1,879 children and their families who had taken part in a completely different study, the Millennium Cohort Study (MCS) and who lived in similar areas that did not have Sure Start.
They found that the children in Sure Start areas:
- exhibited more positive social behaviour
- exhibited greater independence and self-regulation
- were more likely to have received immunisations and less likely to have had an accidental injury - though these may be due to factors other than Sure Start
- provided their children with a better home learning environment
- exhibited less negative parenting
- reported greater use of support services
The comparison was not straightforward, the study points out. The results differed "markedly" from a first evaluation by the same team.
That had indicated that the most disadvantaged families - teen parents, lone parents, jobless households - were doing less well in Sure Start areas than those who were better off.
But this new study provided "almost no evidence of adverse effects".
Their report says their cautious conclusion is that the increased benefits detected in the current study may well stem from improvements in the services being provided and the families' longer exposure to them.
Nevertheless, they say, the positive effects should not be exaggerated as all were modest.
"Clearly it will be of importance to see what the next phase of impact evaluation reveals, as it investigates the functioning of the same children included in this phase of inquiry two years later, when they are five years of age."
Speaking at the first national conference for children's centre leaders, children and families secretary Ed Balls said there was more to do and pledged additional measures.
They include two more outreach workers at each centre in the 1,500 most disadvantaged areas, a review of outreach work to clarify good practice, £7m for more training and guidance on working with black and ethnic minority families.
"Parents bring up children not the government, and this research shows that Sure Start centres can help parents give their children the best start in life," Mr Balls said.
"I want to make sure all families can benefit - which is why we are putting in place a package of measures, backed up with funding and new outreach workers to reach out to the most disadvantaged families."