The school website doesn't like Scratch files! I've no idea why, but they're against the rules. So I've disguised them as text files, which the website is much happier with. To load these files in Scratch, you first need to change the final part of the filename which tells the computer what sort of file it is.
Download the file.
Right-click on the filename.
Right at the end of the filename, change .txt to .sb3
Then you can upload to to the Scratch website to try out.