Just to check if it is unsecured, double click on the Wireless Icon

on your sons machine.
Select 'View wireless networks' and you should get a window something like this:>>>> This

If there isn't a padlock with the wording 'Security-enabled wireless network' next to it, it has no protection.
However if it has your son knows the key. The System will remember this every time it is started and he won't have to input the key again.
This might give the impression of not needing a key in the first place.