NASA says it has selected four U.S. high school teams as finalists in its Balloonsat High Altitude Flight competition.

Officials at NASA's Glenn Research Center in Cleveland, the event's host, said each team's experiment will become the payload aboard weather balloons that will be launched May 25-27. The balloons will rise to the stratosphere, an altitude of approximately 100,000 feet.

One team's experiment will be judged the best.

The finalists and their projects are:

-- Charlottesville High School, Charlottesville, Va.: "The Effects of Near-Space Conditions on Escherichia Coli Bacteria."

-- Upper St. Clair High School, Upper St. Clair, Pa.: "The Effect of Near-Space Conditions on Microbial Life Forms."

-- Stansbury High School, West Jordan, Utah: "Thermal Moisture Penetration."

-- North Carolina School of Science and Mathematics, Durham, N.C.: "Variations on Polyethylene Hard Disk Radiation Shields."

NASA said each team will be responsible for releasing, tracking and recovering its experiments. The teams also will present reports on their findings during the Balloonsat Symposium, to be held at the research center.

An award will be presented to the winning team at their school this fall.

The finalists each received funding for development of their experiment and travel expenses for four students and an advisor to attend the competition at the Glenn Research Center.