Let's break it down:
(1) There is no moral requirement to use extraordinary means to keep someone alive. Neither Scripture nor the Catechism specifically address defibrillators, intubations or CPR as belonging in the category of extraordinary means - but I would argue that the use of defibrillators and CPR at the very least are not extraordinary means in the current context, but rather very ordinary means.
I would think that a ventilator would be extraordinary in the case of an individual who simply cannot breathe on their own. Typically a person who is defibrillated or receives CPR can breathe on their own as soon as they are stabilized.
(2) Whether or not these qualify as extraordinary means is immaterial, because the real question at hand is: is it moral to prevent someone else from helping a dying person?
It is clear from Scripture and the Catechism that coming to the aid of those in distress is not morally prohibited.
(3) And so the moral issue is: do the parents have the moral right to stop a classroom aide from performing CPR on their child? And the answer is: they do not.
You should instead ask yourself this: Is it moral to keep someone alive at all costs? Surely, even you realize that death is inevitable and at some point, fighting it becomes foolish and often cruel.