Many issues here: (1) - Voltage is the wrong variable to measure. Energy is more relevant. He could have charged some rechargeable batteries and see how long they lasted latter with constant load. (2) - The flat array "control", is not built in one plane facing the sun like the commercial ones. It has actually half of the cells in a second plane facing opposite the sun. (3) - The setup is near a house wall, with the tree neared and the flat array farther, and also partly in the shade, reflected light may also confuse results. The panels should be in more controlled insolation conditions for a fair comparison. If the kid had taken 10 minutes to talk to someone who understands solar cells this disaster would have been averted. Doing bad science should not be encouraged !