@gajazi 

@ArcherC8  is right, go to your guest network and schedule the access there. What you can then do is just change the wireless password on your main Wi-Fi.

Here is a FAQ if you want to move forward with configuring parental controls: https://www.tp-link.com/us/support/faq/1145/

@ArcherC8   but doesn't Guest Network only work for WiFi connected devices?  my son's PC is connect to the LAN via Ethernet.  sorry, i should have made that clear.

@Tony  isn't Parental Controls and Access Controls two separate things?  one prevents acces to the internet entirely, and the other is only for limiting particular websites on the web, no?

@gajazi 

You would only go into the access control menu to create a schedule and give it a name, so when you are setting up the parental controls you will choose that schedule in the drop down list. You can leave the all the website entries blank so there will not be access to any site during the schedule time made.

Also, once all the configuration are complete, rebooting the router will need to be done.

@Tony  gotcha.  just so i'm clear... this also means that if my son tries to start up a game that uses the internet, that game won't connect to its servers either?

@gajazi 

Correct, in referencing the MAC address of the device, when ever it tries to pull internet, the router will recognize the address and block the packets (websites, video, etc.).

@Tony   just as an FYI... i got it to work with only using Access Controls (and not Parental Controls).  i created the Schedule within Access Controls (like you mentioned), and then created a Rule also within Access Controls (never activated or used Parental Controls).  and it worked.  i actually found a manual from a different TP-LINK router that was a little more descriptive than the C8 manual was and i was able to figure out a few things more easily from that.

thanks for all your help!