The Cathen article on intention says:
As to the recipients of the sacraments, it is certain that no intention is required in children who have not yet reached the age of reason, or in imbeciles, for the validity of those sacraments which they are capable of receiving. In the case of adults, on the other hand, some intention is indispensable if the sacrament is not to be invalid. The reason is that our justification is not brought about without our co-operation, and that includes the rational will to profit by the means of sanctification. How much of an intention is enough is not always quite clear. In general, more in the way of intention will be demanded in proportion as the acts of the receiver seem to enter into the making of the sacrament. So for penance and matrimony under ordinary conditions a virtual intention would appear to be required; for the other sacraments an habitual intention is sufficient. For an unconscious person in danger of death the habitual intention may be implicit and still suffice for the validity of the sacraments that are then necessary or highly useful; that is, it may be contained in the more general purpose which a man has at some time during his life, and which he has never retracted, of availing himself of these means of salvation at so supreme a moment.
The article on the sacraments puts it succinftly:
In adults, for the valid reception of any sacrament except the Eucharist, it is necessary that they have the intention of receiving it. The sacraments impose obligations and confer grace: Christ does not wish to impose those obligations or confer grace without the consent of man.
It seems to commonly be the case at least in the US, that young teens are raised in at least culturally Catholic families, and are just expected to receive Confirmation around 14 just as they are expected to come with the family to Mass every Sunday; but at least some are just "going through the motions" and those responsible don't do due diligence to ensure each of them are sufficiently prepared and willing.
So if a young person does not really want to be confirmed, but just patiently sits through all the classes, and the Mass and Confirmation rite, can their outward participation (I call this participation "notional consent") be considered sufficient consent to validly receiving the Sacrament?