The frequenting of non-Catholic schools, whether neutral or mixed, those namely which are open to Catholics and non-Catholics alike, is forbidden for Catholic children, and can be at most tolerated, on the approval of the Ordinary alone, under determined circumstances of place and time, and with special precautions. Neither can Catholics admit that other type of mixed school, (least of all the so-called "ecole unique," obligatory on all), in which the students are provided with separate religious instruction, but receive other lessons in common with non-Catholic pupils from non-Catholic teachers. It is necessary not only that religious instruction be given to the young at certain fixed times, but also that every other subject taught, be permeated with Christian piety. If this is wanting, if this sacred atmosphere does not pervade and warm the hearts of masters and scholars alike, little good can be expected from any kind of learning, and considerable harm will often be the consequence (Papal Encyclical, Rappresentanti in Terra, 31 December 1929).