Professors in the US are using TV voting machines (called ‘clickers’) to test students’ knowledge of the subject being taught during lectures. As they vote, bar graphs go up in real time allowing people to see how the voting is going.
Students using the clicker system score 10% higher than without and it seems to level the field between the genders.
Even though the students are not forced to participate in the clicking, 90% generally do. If you add an incentive, 98% do.