The lines get blurred a lot where science should start and religion should end for STEM fields. I am merely pointing out that there are no certainties. For either side. That boy said with 100% certainty that there is no proof of God. And he may be right. But I cannot say that without saying maybe. And no one else should be able to either. And still, no one can say that no proof of something does not discount its existence.
We cannot know without knowing everything. And no one will ever know everything. That's why we can make fun of teenagers so much.