49 This does not prevent the State from making due provision for the right administration of public affairs and for the protection of its peace, within or without the realm. These are things which directly concern the public good and call for special aptitudes and special preparation. The State may therefore reserve to itself the establishment and direction of schools intended to prepare for certain civic duties and especially for military service, provided it be careful not to injure the rights of the Church or of the family in what pertains to them. It is well to repeat this warning here; for in these days there is spreading a spirit of nationalism which is false and exaggerated, as well as dangerous to true peace and prosperity. Under its influence various excesses are committed in giving a military turn to the so-called physical training of boys (sometimes even of girls, contrary to the very instincts of human nature); or again in usurping unreasonably on Sunday, the time which should be devoted to religious duties and to family life at home. It is not our intention however to condemn what is good in the spirit of discipline and legitimate bravery promoted by these methods; We condemn only what is excessive, as for example violence, which must not be confounded with courage nor with the noble sentiment of military valor in defense of country and public order; or again exaltation of athleticism which even in classic pagan times marked the decline and downfall of genuine physical training.
Source: Divini Illius Magistri (Vatican.va)