To block an IP or domain from viewing your site you would just use an .htaccess file in the root directory of your site. If it is coming from a college it could be next to impossible just to block that one person. If they using a computer located in a computer lab then they could simply use a different computer. If they are using their own computer in their dorm they may have a static IP for their computer. However if the school uses a proxy server which is likely the case then you could end up blocking the entire school from viewing it.
Best solution if this person is violating any TOS you have would be to contact the school's sysadmin and report them with whatever information you can collect about the person.
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