It looks like the extension has fallen over. It has not. It is doing exactly what you asked.
What is actually happening
Almost every blocker treats a domain as a family. Block youtube.com and you get everything underneath it too, which is what you want — otherwise a subdomain nobody has heard of becomes a way straight back in.
Here is the part that catches people. Signing in to a Google account is not one request to one address. It is a short chain of hops between hosts, and one of the stops on that chain sits underneath a video domain: accounts.youtube.com. It exists so that being signed in to one Google service leaves you signed in to the others. Your rule cannot tell the difference between that address and the one serving videos, because as far as a domain rule is concerned they are the same family.
So the browser walks into the sign-in, hits the block, and stops. The error your child sees is not "this site is blocked". It is a sign-in that spins, or fails, or loops back to the start — and it happens on the mail page or the classroom page, which you never blocked and never thought about.
That distance is the whole reason this is hard to diagnose. The cause and the symptom are on different sites. A reasonable parent concludes the extension is buggy, uninstalls it, and never finds out that the rule was working perfectly.
You can confirm it in about ninety seconds, and it is worth doing before you change anything. Sign the browser out of the Google account completely, then sign back in with the block still on. Watch the address bar as it goes. If it stalls, and the address it stalled on lives under the domain you blocked, that is your answer, and nothing is broken.
The three places this goes wrong
1. The blocker has no idea what a sign-in is. It sees a hostname and a rule. If the tool has no concept of "this request is authentication, let it through", then every domain rule you write is also a rule about signing in, and you will discover which ones matter on a school morning.
2. You fix it by unblocking the whole site. Understandable, and it hands back everything you were trying to stop. The exception you need is one address wide, not one domain wide.
3. Nobody told the child what happened. They now believe the sign-in is unreliable, which means the next time it stalls for any reason at all, the first thing they will try is turning your rule off.
How to make it hold
Parentech keeps sign-in pages open on purpose. Blocking the video site blocks the videos; the authentication hop underneath it is left alone, so a school Google account still gets into mail and into a lesson. This is not a setting you have to find. It is how the block is built, because the alternative is a product that breaks a school morning and gets uninstalled by lunchtime.
Class sessions work the same way. When a session is running, only the sites you listed will open — and the sign-in addresses a school account needs, so joining the lesson still works even though everything not on the list is shut.
If something else is still failing, the check is the same one from earlier: sign out fully, sign back in with the rules on, and see whether the chain completes. If it does, your remaining problem is on the site itself, not in the rule.
The part that needs you not to be there
Notice when this breaks. Not in the evening while you are cooking. At nine in the morning, on a weekday, when the lesson is starting and you are on a train or already at work and the person holding the laptop is eleven.
That is a bad time to need a keyboard in another building. It is also the moment when a parent's instinct is the most expensive one available: rip the rule out entirely so the class can start, and never quite get round to putting it back.
So the useful capability here is not another setting. It is being able to act during the ten minutes the problem is live. Sign in at parentech.app from your phone, open a site for an hour, take one off the list, start the class session — and it reaches the computer within half a minute, which is faster than talking them through anything.
The honest split: everything above is free on one computer, changed at that computer with your PIN. The family plan is what puts it on your phone and on every other Chrome in the house. If the laptop you are worrying about is the one in front of you, free is the whole product and you should use that.
What this still does not reach
- A site that has genuinely gone down. If the service is broken, no rule of yours will unbreak it.
- A phone or a tablet. Parentech guards Chrome on the computer it is installed on.
- A second browser on that computer. Which is why a standard account without administrator rights matters more than any exception list.
Questions parents ask
Will blocking a video site break their classroom?
No. The sign-in path stays open while the videos stay blocked. That is the specific case this is built around, because it is the one that breaks other tools.
Can I block a subdomain without blocking the whole site?
Add the exact address you mean. A rule aimed at one host stays on that host, and everything under a domain you block stays blocked, so choose the narrower one when the narrower one is what you meant.
It broke once and now they do not trust it.
Fair. Do the sign-out and sign-in test with them watching, on purpose, so they can see the rule holding and the account working at the same time. Five minutes spent proving it beats a term of being blamed for every slow page.
If this is happening to you, one of these usually is too
It worked last month, now it does not · The tab that was already open · Account controls do not reach inside the browser
More on how blocking works: Block websites. Free on one computer — what it costs to reach it from a train.