Participation is, at worst, a system begging teachers to grade-bump their favorites, and, at best, grading students on their social skills, rather than what content they actually learned. Furthermore, it instills the idea that one must be outgoing to succeed in life, to the detriment of introverts.
Some people are more outgoing than others, and people are more comfortable sharing their ideas in class than others. Participation is not a fair measure of the effort one puts forth to learn. Some people are simply too shy to raise their hand in class, and this shouldn’t affect their grade.
Moreover, forcing introverts to speak up in class won’t make them more gregarious; rather, it will make them feel that their personality is somehow wrong when it’s really just a part of who they are.
Grading on participation will also encourage people to talk for the sake of credit, rather than to contribute to meaningful conversation. Rather than having student parrot each other in a long discussion, teachers should foster a safe environment where students don’t feel pressure to speak up, but can do so if they want.
Elementary schools don’t grade participation, nor do colleges, yet high schools do.
The purpose of school is to prepare you for the real world, and how teachers calculate grades should reflect this. Students should spend their time studying rhetorical devices and the causes of World War I, not on gathering up the courage to raise their hand and stressing about how their level of participation may be affecting their grade.