When you are using SchoolProxy.co to browse the web, you're not actually connecting to your target site but instead, the web proxy is and hence helping you to browse anonymously. School Proxy is more suitable for people who would like to browse while hiding their presence.
In most cases, schools, work places and other institutions tend to block access to certain websites. Fortunately, such sites can only be accessed via a proxy server by helping the user to bypass an ISP proxy. Basically, proxy browsing sets your browser to use another proxy server.