The pupil premium was the first piece of policy the two parties agreed upon during the early negotiations that forged the Con-Lib coalition, but how it will be implemented is still mired in confusion.
Unveiling their plans for the new Government, Prime Minister David Cameron and his Liberal Democrat deputy Nick Clegg highlighted the policy, claiming in their foreword to the coalition agreement that it would allow the poorest students to go to the "best schools, not the worst".
If introduced, the pupil premium will provide an additional fixed sum of money that will be made available to schools for every disadvantaged pupil they accept.
The money could be spent on anything from higher wages to attract better teachers, to improved facilities.
Before the general election, the Conservatives suggested they would pay for the policy by adopting a single national funding formula that would incorporate a pupil premium. Meanwhile, the Liberal Democrats pledged #163;2.5 billion for the policy, to be paid for by scrapping tax credits for families on above-average incomes.
The coalition agreement states that the new government will fund a "significant premium for disadvantaged pupils from outside the schools budget by reductions in spending elsewhere".
According to Haroon Chowdry of the Institute of Fiscal Studies, who authored a report on both the Lib Dems' and the Conservatives' approach to the pupil premium, the Coalition's take "falls between two stools".
"The #163;2.5 billion figure is very notable by its absence, so we are not sure what the total is going to be, but I would say it is likely to be less than #163;2.5 billion," Mr Chowdry said.
"Although it (the agreement) says it will be funded from outside the schools budget, it might come from other areas of the education budget, such as killing off (the online directory of support services) Contact Point - it's the way it's worded."
"We already know that dropping tax credits for above-average income families is going to be used to fund the deficit reduction, so it's not quite Lib Dem policy and it's not quite Conservative," he added.
It is expected that the pupil premium will not be rolled out until at least September 2011. But Mr Chowdry believes the coalition may push it earlier.
He said: "It has been the headline education policy of the Lib Dems and it was on the first draft of the coalition agreement, as well as being the first piece of policy the two parties agreed on, so it is unlikely it will take too much time."