Repl.it Classroom Pro is free for Public Schools. Here is a non-exhaustive list of schools that fall under that category...
Additionally, if you are a non-profit organization that teaches programming and cannot afford our services, please let us know and we can figure something out.
The application link will be available soon.
Please note that for an account to be under the Public School plan, you must use an email that belongs to your domain and the email must be verified.