The Create App for Chrome OS used to require a paid subscription but is now free of charge.
Opening the Web Editor without the Create App will trigger an installation prompt.
Install the Arduino Create App (Chrome Web Store).
If a yellow banner is displayed, the Web editor could not detect the Create App. Make sure it is installed.
School computers and networks may restrict installation. Contact your local IT administrator for help.
The Web editor will detect the Chrome App automatically and you start writing and uploading code to your board.
Since the app is now free, there is no longer a need to sign up for a subscription plan. Simply have the Create App installed on each computer, either by the students themselves or by an IT administrator.