Depending on how you connect to the net, some home routers/firewalls available allow you to block ports with a number of smart filters.
Filters can include the type of connection to the router, destination network, subnet, and time/duration of the connection.
This would be a fairly standard home wireless/ADSL router, 4 hard wired ports, WAN, and wireless, normally have a web based configuration tool that is password based.
Another option, if you want to promote an atmosphere where they have to take responsibility for their actions is to use something like
CommView for WiFi is not to actually block the ports, but monitor the activity by machine, protocol, and time of use.
Just giving you options and information.
