Weekly philosophy sessions in class can boost primary school pupils' ability in maths and literacy, a study says.
More than 3,000 nine and 10-year-olds in 48 UK schools took part in hour-long sessions aimed at raising their ability to question, reason and form arguments.
A study for the Education Endowment Foundation (EEF) found pupils' ability in reading and maths scores improved by an average of two months over a year.
For disadvantaged children, the study found writing skills were also boosted.
The trial of the Philosophy for Children programme (P4C) focused on children in Years 4 and 5 - aged nine and 10.
It was part of efforts by the charity, EEF, to evaluate ways in which schools are spending pupil premium money beneficially on children from poorer backgrounds.
The disadvantaged pupils in the trial, those on free school meals, saw their reading skills improve by four months, their maths by three months and their writing ability by two months.
Lead researcher Prof Stephen Gorard, from the School of Education at Durham University, said: "Our results suggest that these philosophy sessions can have a positive impact on pupils' maths, reading and perhaps their writing skills.
"But crucially, they seem to work especially well for the children who are most disadvantaged. This is very encouraging as we, along with the EEF, are committed to helping tackle educational disadvantage.
"Evidence like this is extremely important in identifying what works and what doesn't, and to help head teachers decide how to spend their pupil premium funding for most benefit to their pupils."
The findings could have added significance because research has shown that many interventions aimed at helping disadvantaged pupils to catch up actually boost their more advantaged peers as well.
This can make it difficult to close the gap in achievement between rich and poorer pupils.
The study said that, at £30 per pupil, P4C could be a cost-effective way for schools to spend their pupil premium money.
Teachers also reported a beneficial impact on pupils' confidence, patience and self-esteem as well as their raw results from the philosophy classes.
In a typical session, pupils and teachers sit together in a circle. The pupils are shown a video clip or newspaper article to stimulate their interest in a subject. This is followed by a short period of silent thinking time.
The class then splits into pairs or small groups to discuss questions on the subject before coming back together for a whole-class discussion.
Subjects covered included whether a healthy heart should be donated to a person who has not looked after themselves.