Some school networks block students from viewing sites like YouTube.
Proper school network configuration can help to ensure that educational videos are available to students and teachers. Please send this this link to the school's IT team if students or teachers encounter difficulties when playing embedded videos.
Some web filters and firewalls, such as Zscaler, require users to log into Zscaler before they can watch YouTube videos. This may need to be repeated each day to access Youtube.
If the school expressly forbids students from viewing videos on YouTube or Vimeo, then the most common alternatives are for students to watch the videos at home, or for the teacher to project the videos for the whole class.