These principles with due regard to time and place, must, in accordance with Christian prudence, be applied to all schools, particularly in the most delicate and decisive period of formation, that, namely, of adolescence; and in gymnastic exercises and deportment special care must be had of Christian modesty in young women and girls which is so gravely impaired by any kind of exhibition in public.

Four Great Encyclicals: Labor- Education- Marriage- the Social Order (ed. 1900)