If you would like to filter your student's web access more strictly than the District's existing web filter, you can install and configure the Block Site chrome extension on their school-issued chromebook.
First, install the extension on your student's chromebook by going to this link:
https://getblocksite.co/chrome
Click the Add to Chrome button in the top-right corner of the page, then click the Add Extension button.
A new page will open with the following message. Click the I Accept button to continue.
Next you will be prompted to "Choose a plan". However, you can use this extension for free: click the Skip button in the upper-right corner of the page.
You will be taken to the BlockSite settings page. I recommend setting up Password Protection first. Click Password Protection in the left sidebar.
Check the box marked Protect your preferred BlockSite options..., and then enter your personal email address and select a password. This password is not your email password, but the password you will use to unlock the Block Site extension when you want to make changes. Click the Save button and you will be emailed a verification link.
Important: Due to the restrictions on student chromebooks, this verification link can be difficult to use. The link must be opened on your student's chromebook, not on another computer. DO NOT click the Verify now button in your verification email on another computer.
Instead, copy the link from the Verify now button in the verification email, and open it on your student's chromebook. You can do this by right-clicking (or holding the control key while clicking) the button and choosing Copy link address. The link will look something like this: https://blocksite.co/verify-link.php?eid=13a1bfc1daea7bb0554e846912d06680.
Instead of typing this entire address into your student's chromebook, visit https://bitly.com and paste the link into the Shorten your link text box.
Then click the Shorten button to generate a link which looks like https://bit.ly/******.
This shorter link will be much easier to type in on your student's chromebook. Open a new tab on the chromebook, type in this link, and press Enter. You will see a message that your email address has been verified.
Now, when you return to the Block Site extension's settings, you should see a message that your email address is verified. You may need to reload the page. I would also recommend checking the box marked Get notified via email when BlockSite is uninstalled.
You may now configure your filter settings to block or allow sites for your student. Click Block Sites in the left sidebar to specify which sites you would like to block. If, instead, you would rather block all sites except those you specify, click the Whitelist mode checkbox on this page.