On 17th May, 1852, Blessed Pius IX issued the second of his Encyclicals of that year on the subject of the discipline of the Clergy, entitled Probe Noscitis Venerabiles, which was addressed to the Archbishops and Bishops of Spain.
"2. Devote your constant thoughts and efforts to those who have dedicated themselves to the sacred ministry. See that they remain mindful of their vocation and direct their manner of life according to the standards of the sacred canons and ecclesiastical discipline. They should glow in the gravity of their character, the sanctity of their life, and the praise of their wholesome doctrine. They should also give an example of all the virtues to the Christian people; perform the duties of their ministry fully, skillfully, and religiously; and labor zealously for the salvation of souls. The young clergy, even from their earliest years, should be guided opportunely toward piety, virtue, and an ecclesiastical spirit. See that they are diligently taught literature, especially the sacred disciplines, untouched by the danger of any error. The faithful entrusted to you should be nourished daily with the words of faith and strengthened by the spiritual gifts of grace so that they can grow in the knowledge of God and walk in the ways of the Lord; they must never permit themselves to be deceived and led into error by the manufacturers of lies and the followers of perverse dogmas. Since, however, as each one of you well understands, nothing contributes more to the preservation of sacred and public affairs than the proper education of youth. Therefore, watch carefully that in all the public and private schools a doctrine entirely Catholic is taught and that the young people are trained scrupulously according to the precepts of our holy religion."
Probe Noscitis Venerabilis, No. 2