How to prevent my children from playing Xbox using my parent account, after I sign in to...

My hero! OMG, this totally solved the problem. I wish I knew about it sooner. Thank you for the quick fix!

Set the console as your home console in order to share the Gold with them so you don't need to sign in at all. Then make sure the preferences in your account settings are set to require a password to sign in. https://support.xbox.com/en-US/help/hardware-network/console/my-home-xbox

To add to what has already been said (assuming that the parent has the Xbox Live account) set the Xbox that the children will be using as the Xbox Live Account holders (parents) "My Home Xbox" then the parent account can sign out and the children can use
the Live and any games (deemed suitable) that are on the parent account. You as the account holder can then sign in on the other Xbox and use that to play your games and use Live

Kujawafamily,

You should put a passkey on your account. https://support.xbox.com/en-US/my-account/security/create-xbox-one-passkey

Here’s just a few benefits of having a passkey on your account:

• A passkey protects against a child signing in as the parent and overriding parental controls. A personal passkey prevents a child from simply clicking on the parent’s picture, signing in as the parent, and changing the child’s otherwise
  parentally controlled settings.
• A passkey helps to prevent unapproved charges. You can choose to require a passkey to make any purchase on Xbox Live. Setting a passkey helps prevent children from making unapproved purchases.
• A passkey allows the parent to grant content exceptions. The only way for a parent to override a content limitation is by entering his or her personal passkey, so it’s easier to manage what content your children can see on your console.

Thanks for the replies!

So when your son is able to sign into the account on the days that it is set to blocked is it possible that there is also an adult account signed in even though its not being used. If a parental account is signed in at the same time as the child account
then it assumes that the child account has permission since they are playing together. If the child has figured this out you can Set up a Passkey
to prevent the parental account from being signed in.

A passkey protects against a child signing in as the parent and overriding parental controls. A personal passkey prevents a child from simply clicking on the parent’s picture, signing in as the parent, and changing the child’s otherwise
parentally controlled settings.