Almost £7 million a year could be saved through changes to how children are transported to school, it has been claimed.
Around a quarter of pupils use education board buses and Ulster Unionist education spokesman David McNarry said the existing policy was "out of date".
Around 110,000 children are transported to school in Northern Ireland. Many of the routes which education boards run are not commercially viable, including rural areas or for children with special educational needs.
Mr McNarry said: "We simply cannot afford to ignore potential savings. The least we can look for is a far better working relationship between the education boards and Translink (public transport company), for the benefit of the public purse and to see what reductions can be negotiated with commercial private companies, using the negotiating tool of bulk purchase.
"We should enlarge the scope of private enterprise to compete for contracts, or bundles of contracts, and see what enhancement of community bus services can also be raised on the back of this."
Mr McNarry said 30% of children receive free transport with an annual cost of £74 million. Around 65% use Translink and 27% use education board buses. He said if all pupils on board buses were transported by Translink an annual saving of £6.8 million was possible.
Education Minister John O'Dowd wants to identify rural schools which are no longer viable and could be closed.
Mr McNarry said: "If rural schools are closed by the executive action of the minister he must be responsible for the financial consequences of his actions. This includes the cost of forcing many more children into a position where they will need home-to-school transport to travel to more distant schools."
Mr O'Dowd said Translink and the boards play complementary but different roles in school transport.
"Translink's unit costs reflect their provision of routes that are commercially viable. Board unit costs reflect their provision of routes and services that Translink may not commercially provide (e.g. many rural routes, the majority of the services provided for statemented children). Comparisons between the two are not like-for-like."