Permission slips for class trips might become a thing of the past if Google has its way. The company has announced that it's expanding its free Expeditions program -- the virtual reality version of the old-school class trip -- to places that include the Great Barrier Reef in Australia and Buckingham Palace.

Initially conceived as a separate kit that would be sent to classrooms, this new take on the software will provide a dedicated Android app for schools that will allow students and educators to take trips across the globe, without ever leaving the classroom.

Since its launch last year, Google's Expeditions Pioneer Program reports that 500,000 students in the United States, Sweden and Canada have used the system. To gain entry into the free program, an interested school must apply via the Expeditions website.

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Once a school is approved to enter the program, Google sends over the kit, which is comprised of the (beta) software and VR headsets (such as Google Cardboard or Mattel's View-Master VR). The teacher can then guide up to 50 students. The schools also receive routers in case there's no reliable Internet connection.

After everyone is connected, the trip leader can conduct tours of Machu Picchu in Peru, Antarctica or even the surface of the Mars -- places a regular school bus would be unable travel. Google has added two more Expeditions to its roster. The first will take students on an 360-degree tour of Buckingham Palace. The second trip will take students under the sea to explore Australia's Great Barrier Reef.

Many think of gaming when they hear "virtual reality," but efforts like Expeditions will help turn the medium into a powerful educational tool, especially for underfunded school districts.