Minecraft problems with macbook air?

The ICT people at my school just restarted my MacBook Air, which of course deleted everything. I re-download minecraft (while still at school), but it doesn't work. It keeps on saying "Unable to download remote file. Check your internet connection/proxy settings." What should I be looking for in my settings? Why won't it work? Please help. My internet connection seems fine, and there's no weird proxies added.

Your school blocks files from being downloaded 9/10 times. Download from a different Wi-Fi source and you are fine