From the 2004 Instruction Redemptionis Sacramentum at
http://www.vatican.va/roman_curia/c...doc_20040423_redemptionis-sacramentum_en.html
“[87.] The First Communion of children must always be preceded by sacramental confession and absolution.
[169] Moreover First Communion should always be administered by a Priest and never outside the celebration of Mass. Apart from exceptional cases, it is not particularly appropriate for First Communion to be administered on Holy Thursday of the Lord’s Supper. Another day should be chosen instead, such as a Sunday between the Second and the Sixth Sunday of Easter, or the Solemnity of the Body and Blood of Christ, or the Sundays of Ordinary Time, since Sunday is rightly regarded as the day of the Eucharist.
[170] “Children who have not attained the age of reason, or those whom” the Parish Priest “has determined to be insufficiently prepared” should not come forward to receive the Holy Eucharist.
[171]Where it happens, however, that a child who is exceptionally mature for his age is judged to be ready for receiving the Sacrament, the child must not be denied First Communion provided he has received sufficient instruction.
[169] Cf.
Code of Canon Law, can. 914; S. Congregation for the Discipline of the Sacraments, Declaration,
Sanctus Pontifex , diei 24 maii 1973: AAS 65 (1973) p. 410; S. Congregation for the Sacraments and Divine Worship and S. Congregation for the Clergy, Letter to the Presidents of the Bishops’ Conferences. Episcoporum,
In quibusdam , 31 March 1977
: Enchiridion Documentorum Instaurationis Liturgicae , II, pp. 142-144; S. Congregation for the Sacraments and Divine Worship and S. Congregation for the Clergy, Response to dubium, 20 May 1977: AAS 69 (1977) p. 427.
[170] Cf. Pope John Paul II, Apostolic Letter,
Dies Domini , 31 May 1998, nn. 31-34: AAS 90 (1998) pp. 713-766, here pp. 731-734.
[171] Cf.
Code of Canon Law ,can. 914.”