It was argued the schools charged high fees, but did not offer enough support to those who could not afford to pay them.
Legislation was introduced by the Scottish Parliament in 2006 to tighten up control of charities following scandals involving cancer charities.
The new rules meant charities must show they have a charitable aim, such as providing education, but also that they have a wider public benefit.
In the case of independent schools, where the benefit is only provided to a section of the public, the charity must show it does not operate unduly restrictive practices, such as overly high fees.
In October 2008, the Office of the Charity Regulator (OSCR) determined that in the case of each of the four schools, the charity test was not met. Each was issued with a three-part direction that required them to confirm their intention to meet the test.
It also meant providing OSCR with a plan setting out how the schools intended to address the issues which had caused them to fail the test and to demonstrate that they had implemented their proposals by October 2011.
At the time of the OSCR ruling in 2008, just two of the 583 pupils at Lomond School in Helensburgh received means-tested assistance, while at St Leonards fewer than 1 per cent of pupils received help.
According to the OSCR, its investigation has led to significant improvement in that situation.
The regulator’s chairman, Dr Graham Forbes, said one of the four schools had seen the proportion of pupils receiving financial support rise from 3 per cent to 10 per cent.
Of the 23,500 charities in the Scottish register, there are 58 schools, which are also members of the Scottish Council for Independent Schools.
To date, OSCR has assessed 12 independent schools. Of these, six met the charity test and five (including Hutchesons’, Merchiston, Lomond, St Leonards and High School of Dundee) were issued with directions and subsequently met the test. High School of Dundee met the test in 2007. Another school, Cargilfield, is under review.
According to OSCR, fee-charging schools remain a “priority group” for its ongoing work.
Simon Mackintosh, a partner at law firm Turcan Connell, said: “The decision on the four Scottish schools brings welcome clarity to the Office of the Charity Regulator’s approach to public benefit.
“There is a lesson for the wider charity sector – if the costs of your services are high enough to deter a substantial proportion of the population from benefiting, then you need to make arrangements to widen access”.
Despite the economic downturn, Scotland’s private schools have seen rolls remain largely stable over the past year.
Gordonstoun, which charges around £30,000 a year for boarders and £20,000 for day pupils, this year recorded its fullest school role since the early 1990s.