The Chrome extensions feature is currently under review by GCVS to limit student ability to install extensions on Chromebooks. Poorly made or malicious extensions cause the most calls in to support and cause issues with stability in the Chrome web browser.

Chromebooks by their very nature are very stable and secure. The single biggest contributor to issues with Chrome crashing, locking up, changing to a black screen, pop-ups, or rebooting the Chromebook are tied to malicious or poorly made extensions for the Chrome browser. These can often interfere with Blackboard as well. They often get install under the pretense of being part of a game or theme, but include annoying popups. 

If your Chrome browser or Chromebook is suffering from issues such as above you most likely have some rogue extensions installed. Here is how to check for them and remove them. 

To take a look at all of the extensions installed in your Chrome browser:

In your browser click on the 3 stacked dots in the upper right hand corner, right under the X to close the window (1). Then go down to 'More tools' and click on that (2). Then over to Extensions and click on that (3).

That should open a window like what you see below. These are the extensions that are installed under your Chrome browser. The below example is what it should look like on a new Chromebook without any student installed extensions. 

Any sliders with a light blue slider like in example (3) below are installed and managed by the school. They are from reputable sources and have been tested against causing problems and can be considered safe, You cannot remove or disable these. 

Any sliders that are dark blue like in example (4) are either pre-installed by HP or have been installed by your student. Clicking on the slider will turn it grey, and turn off the extension. You can also click the Remove button to uninstalled the extension completely which is recommended. Unless you absolutely require it for School you should remove extra extensions down to the basics you see below. Too many extensions can cause issues too.