[Locke1689]

You have made a logical fallacy sometimes known as the is-ought fallacy or is-ought problem.

The key point is that the parent is stating that things ought to work a certain way. While your statement that things are a certain way may be true, it is actually a non sequitur in relation to the ought proposal.

If you wish to make a cogent argument you'll need to address the ought section of his argument or connect your "is" statement to be no longer orthogonal.