If something is participatory, it allows or requires you to participate, or join in. In high school, classes are participatory: they require you to join in by doing your homework and taking part in discussions.
Education research shows that participatory lessons, or lessons in which the students participate in their own learning, are more effective than direct instruction. For example, a participatory activity in which students take a classroom poll of favorite fruits and analyze what percentages of the class like which kinds is much more likely to stick with them than a non-participatory lecture on percentage.