The two Year 6 pupils at St Mary's Roman Catholic school in Bicester set up a complex experiment where they observed both all-boys and mixed football games set up specially at their school, with questionnaires both before and after the matches.
They found that boys played differently in the mixed game - they were less rough - but they didn't take over. "The boys surprised me because I thought they would just stick on their own, but they did pass and play as a team with the girls", says Ben, 11.
Mary Kellett, the children's research supervisor from the Open University, is thrilled by their multi-method approach, while Jane Paterson, the link teacher from their school, is "quite staggered by how well it's worked".
The project has given them a chance to fly, she says.
Their class overwhelmingly favoured mixed men and women's premier league football, and preferred to play in mixed teams. They thought mixed football would improve spectators' behaviour and that it would encourage people to be more social.
To double-check their results, Ben and Selena asked the questions in both positive and negative ways. Then the results were sent to the FA, FIFA and Oxfordshire Football Association, with questions about whether they might one day change their policies.
"By using the kids' football we are trying to show it's not illegal to play together," says Ben.
What did they learn? "With me it's improved my range of vocabulary," says Selena. "In six weeks we learned how to pick out all the finer detail out of things that maybe people wouldn't notice and draw them into a conclusion."