Education ought to be a means of providing children with equality of opportunity.

That is the aspiration of most policy-makers, but unfortunately in reality some children have advantages over others right from the start. Deprivation, family breakdown and parents' ability to afford private schooling are just some of the factors known to impact on children's attainment.

Once children have sat an exam, however, the same rules ought to apply to all. Any appeals to the Scottish Qualifications Authority (SQA) should be made on the same basis. A child's parents' ability to pay for an appeal should have no bearing on whether an appeal goes ahead. Appeals across the schools system should be based on teachers' professional view of the whether there are legitimate grounds. Parents should have some say, but not dictate whether an appeal goes ahead or not. It would clearly be unfair if pupils from private schools could more easily appeal disappointing exam results than pupils from state schools.

But that is apparently the case. It has emerged that some independent schools are allowing parents to fund the appeals process for their children even if teachers advise against it, in contrast to the state sector, where it is very unlikely parents will be allowed to do so.

It is not the state sector's approach that is at fault here. It would obviously create inequalities if parental funding of appeals were permitted, since there is huge variation in the financial means of state school pupils' parents. Though the charges only apply if there is no change to the pupil's grade and are not huge - £10 for a check to see if the marks have been added up correctly to £39.75 for a full marking review - for parents struggling on low incomes they are unmanageable.

An additional problem for the state sector is that comprehensives are bearing the full cost of appeals where those private schools that allow parents to pay are not. So if a state school judged in a given year that a dozen results should be fully reviewed, the potential cost if those bids were unsuccessful would be £500. There are not many schools that have such cash to spare, so it might put pressure on them to limit the number of appeals. Private schools passing that cost on to parents, by contrast, would face no such pressure.

If a private-school parent self-funds a successful appeal under the new system where a state school pupil would not have access to the same opportunity, then the system is giving certain private-school pupils an unfair advantage. The principle that the school should pay ought therefore to apply equally to all schools.

Fewer than half of appeals made last year were successful, but given that tens of thousands were, and given the divisiveness highlighted here, some would argue there should be no charge for appeals. If they cost no school or parent anything, then this problem would not arise. It remains to be seen how many appeals there are under the new system and how they split between state and private-sector schools, but it looks as though an inequality has been built into the system that needs to be addressed.