Google is unlike other popular search sites, such as Alta Vista and Yahoo, which in recent years have turned themselves into gateway, or portal sites that offer access to searching as well as other popular web activities such as shopping and online banking. For schools, Google has more advantages than just efficiency.
Many other search engines include advertising in the results they return. So a search on covection, for example, on a search engine such as Ask Jeeves, may include in its results links to websites that are paying to be displayed on the page and which have nothing to do with what the student is looking for.
Google's accuracy also helps it guard against duping by developers of web pages, who have cultivated techniques for increasing the likelihood of their pages being returned in search results. One common trick is to add references to current events in websites that would otherwise be blocked.
Depending on how the search engine operates, this can improve the odds for a site being returned when users enter Euro 2000, Columbine or whatever is the topic of the day, in the search engine.