This is an occasional problem with Google (and some other search sites). Some sites pretend to be search sites but actually just pass your search off to sites like Google and then pass the results back and Google, understandably, does not like that and attempts to block it. Every connection from your school goes out showing the same IP address. That is required by our Internet provider in order to conserve public IP addresses. As a result, if your school is very active on Google over a short period of time, Google may perceive that as an attempt to run a search robot against Google's search engine and they block the traffic for a while.
The problem usually disappears within 15 minutes and unfortunately there is nothing we can do to prevent it or force it to clear up more quickly. Some recommended workarounds:
Article ID: 391
Created On: Mon, Apr 19, 2010 at 2:03 PM
Last Updated On: Tue, Dec 30, 2014 at 10:31 AM
Authored by: Maija Stein
Online URL: https://kb.nsd.org/article-391.html