I saw this competition advertised on https://goo.gl/kUCf1c   It seems to be open to the world to 13-18 year olds!  The submission deadline is Wednesday, October 7, 2015, at 11:59 PM ET.

As long as your students are 13 or older at the time of registration and no older than 18 by October 7, 2015, they can participate. The organisers welcome submissions in English from everyone who meets the age requirements, including students who are homeschooled, students with disabilities, and students from all over the world. For additional details, check out the rules.

What do you have to do?

The Breakthrough Junior Challenge presented by Khan’s Academy and Breakthroughprize invites you to share your passion for math and science with the world! Submit a 10-minute video that illustrates a challenging concept or theory of mathematics, life sciences, or physics in an engaging, illuminating, and creative way.

You can explain an age-old theory or concept or a more recent breakthrough discovery, including one made by a Breakthrough Laureate or perhaps even by you! The winner will receive a $250,000 post-secondary scholarship!”

The winning prize is amazing! Visit https://goo.gl/kUCf1c and register.