Schools which open late and offer out-of-hours clubs are good for children's self-confidence, a survey by the education watchdog Ofsted suggests.
Out-of-hours sports clubs are on offer to children
The government's extended schools programme for England also appears to have improved exam results and parental involvement in education, it adds.
But the survey of 20 schemes in 16 areas found funding was sometimes too short-term to allow effective planning.
The government said extended schools were having a "positive impact".
'More positive attitudes'
Ministers are putting £680m up to 2008 into the scheme, which involves extending hours until 6pm and encourages bodies such as universities and sports clubs to provide activities.
Parents are also urged to take up courses and involve themselves in their children's education.
Ofsted found extended schools had fostered "more positive attitudes" among pupils, who were "keen to remain after school to work and relax".
They had developed a "greater sense of ownership" and were "proud of the school".
One comprehensive had doubled the number of pupils getting five A* to C grades at GCSE within two years of extending hours.
Ofsted found most parents were positive about the changes but that, in some places, it was unclear whether they were "seen as integral to creating services or were simply consumers of them".
Schools had, though, become a "hub" for communities.
Miriam Rosen, Ofsted's director of education said: "Most extended services are meeting the needs of children, young people and the wider community.
"They are giving users more self-confidence, helping them to develop better relationships with family members and peers and raising their aspirations and attitudes to learning."
But inspectors found "very limited spending periods" for some grants, which limited the breadth and depth of services.
Finances were complicated by having to account for each service separately, rather than for the programme as a whole.
Ofsted said local authorities should provide a "strategic overview" to ensure provision "developed coherently".
Children's Minister Beverley Hughes said the report highlighted the "positive impact that extended activities have on behaviour, attendance and the attitudes to learning of pupils.
"It has also found that in those schools where it is being monitored there has been a direct impact on raising standards."
She added: "I believe that extended activities and children's centres are central to our wider reforms of children's services and education and this report provides further evidence of their importance."