Pretty recently I came across an article called "Help Shy Kids-Don't Punish Them" and it's very good at explaining the various ways in which you can encourage kids who are apprehensive about speaking in class to share their opinions without putting them down, randomly calling them out, or punishing them.
Do I think that shy kids should learn to speak up in class? Yes, I do. Everyone has to step out of their comfort zone once in a while, and learning to assert yourself verbally can be a powerful life skill.
The person who wrote the original article suggested methods that can be used to benefit shy people. She suggested that when a teacher brings up a topic to discuss in class, she gives each student time to write down their thoughts in advance before presenting because some people may find it easier to gather their thoughts on paper before saying them out loud.
For shy students, another method is to bring up a topic and allow some time for every student to discuss their idea with one person before bringing it up to the entire class, just so they get time to think of an idea first and share it with a friend so they can become comfortable talking about it. Kind of like a test run.
These aren't necessarily revolutionary. Most of my teacher already use methods like the ones mentioned in the article, and speaking from personal experience, I've seen the results. Shy kids grow bolder, and introverted kids are happy with the chance to express their opinions in writing or work on projects on their own if it's an option for them.
For example, my 9th grade English teacher had these things called seminars. The class basically gathers in a circle of desks and people have the option to share their opinion on a certain theme in the book we're reading. The teacher had us split up into groups of three. He gives us at least three days to do our own research so we have some stuff to say. Then the teacher asked us a question and allowed us to talk about it among our three people and then share it with the class. I think this system is great because it gives us time to prepare. The teacher also didn't call on anyone or force them to speak, but allows them some time to collect themselves so they can do it on their own.
If you're talkative, you should be given a verbal outlet in class. For kids that work better in a group, there should be more group and partner based work.
But if you don't communicate as well verbally or like working on your own better, there are also methods that can help kids in those situations.
Learning to speak out is important, expressing your opinion is important, and so is learning to work with others, but learning to communicate through writing, working as an individual, and knowing when to sit back and listen instead of speaking is also important. Ideally both skills should be focused on and students should grow stronger in whichever set of skills is their weak point. Surely both skills are equally important, and being good at talking doesn't make you "better" than someone who is more proficient in writing as opposed to verbal skills.
For instance, if you are bad at math and struggling in it, shouldn't it be an obvious thing that you get help for it? It's one thing to get bad grades for not trying hard enough, but if you're actually not good at something people will tell you, but they'll also give you advice on how to get better. Simply saying "you're bad at math so you get an F" doesn't help. The same applies to class participation.
Bad grades are generally not used as punishments. They indicate that you either need help in something, or you're not trying as hard as you should. If you except to get better at something, you have to want to. In any case, shy kids do need to try if they expect to be more confident, just as kids who talk too much do need to try to not call out as much in class. Effort is always involved, but so is help.
I don't have a problem with class participation being graded, but just like with anything else, kids that struggle with it do need advice and help. How much you say also shouldn't be the importance of the grade. It should be what you say. A kid who says a lot but doesn't really contribute to the conversation shouldn't get a better grade than the kid who says less but adds a lot to the topic.
Implementing new methods for helping quiet or shy children or bringing out their strengths is not about making exceptions, just like using different methods for bringing out the strengths of more talkative children is not about making exceptions. The shy kids that really want to talk more may find that they are comfortable talking a lot and enjoy doing so if they are in a comfortable environment. The important part is that the focus is on help and not punishment.