I'd add another vote for NOD32.
I'd also recommend
K9 Web Protection if he wants to install some content filtering software to prevent his 13 year old from encountering any of the less savoury content the internet has to offer.
I've used it on my kids PC's for a couple of years now. It blocks inappropriate content very effectively, has lots of configuration options so you can block sites depending on their content (e.g. porn, gambling, violence etc.), and has very few problems with false-positives (i.e. blocking a site which is actually OK). Best of all it's free.