How do I block an iPod from connecting to wifi without resetting a password

I want to block a specific iPod from connecting to my wifi. I set a password already but for good measure I want to know if I can disable connectivity altogether even if the owner figures out the password. I read some time ago that I can go online and enter the MAC address which will permanently block the device, I did that already and set a password for the entire network too but I also want to know if the iPod will still be blocked even if the owner gets the password that is set for all devices. Sorry if it's a stupid question but I wish Internet providers and Apple came up with a solution where specific devices can get blocked for good without the use of a password.

By the way, the iPod I want to block can still detect my network but can't connect because of the password, does that happen even if you block the device's address through your network?