Many high schools have "firewalls" built into their internet networks that automatically block you from accessing or downloading anything but a few applications and sites that have been pre-approved by your school. (In general that's a good thing, because it keeps out the creepers and the bad guys.)

You might have to talk to your college counselor about having your school's IT administrator or IT department "whitelist" https://www.inline.com, and https://inlinecoach.com from the firewall (i.e. make an exception to the firewall) so that you can access Inline and use it while you're on your school's internet network.