We now self-host all of our skills videos on the site by default (although you may choose to change to YouTube- see the related article at the bottom of the page 'Want to switch to Youtube? Here's what you should know'). We also use Vimeo for some of our help videos.
Whichever you use, it is possible that your IT manager may need to allow the videos to play in your school.
In order to allow the videos, you will have to get your network/IT manager to whitelist the URL "videos.hegartymaths.com/*".
If you are using Youtube, write into us at firstname.lastname@example.org, and request the Youtube whitelist. Your network manager can use this to whitelist all the URLs associated with our videos.