The busiest is likely to be VT, formerly Vosper Thornycroft, the UK's leading builder of warships. It has an expanding education wing, which provides careers guidance for teenagers, vocational courses in subjects such as engineering, and financial and management services for schools, including more than 80 in Surrey.
VT hopes to become a key player in the Building Schools for the Future programme, which will rebuild secondary schools across England.
Phil Rood, VT spokesman, said: "We have never made a secret of our defence work because we are proud of our heritage. We think there is a synergy between defence and education because both involve a great deal of negotiation with the Government."
Another UK company is Qinetiq, which develops cutting-edge military technology, including missiles and "electrothermal chemical guns". It has been selling a handheld electronic registration system to schools for more than a year to help them tackle truancy and runs a range of projects to encourage children to learn about science.
Raytheon, a US defence company which created weapons including the Patriot missile, has also been trying to promote interest in science among primary school children in Harlow, Essex and in Fife by arranging visits by a wacky scientist called "Professor Bonkers".
Ann Widdington, a consultant to Raytheon, said: "We are pushing maths and science because there is a dearth of engineers. There is more to Raytheon than missiles."