Professor Haldane, director of the centre for philosophy and public affairs at St Andrews University, said his experience of independent Catholic schools in Washington and Virginia had convinced him that parents had to be more involved, "not just notionally, but quite actively, in sustaining them".
He had reservations about the value of Catholic schools in Scotland ending up within the state system but accepted that there was "no going back for us in the immediate future".
In the United States, Catholic schools were largely run by the parish and community and were "immensely strong" for it.
Furthermore, fees were low. "Parents feel a deep commitment, they feel it's their school and involve themselves in various ways," the professor told delegates.