The core issue here is that teachers should communicate with students in class or send them emails. The decisive factors relating to this topic mainly lie in two aspects. One is which way will make teaching process more efficient, and the other is which way will make the students learn more knowledge. After examining the above aspects carefully, I find it's better for teachers to encourage their students to express their ideas in class, and the reasons are as followed.
I concede that too much talks between students and the teacher will disturb the normal teaching plan and even cause some contents to be delayed. But does this mean that teaching become less efficient? Of course not. The main purpose of education is to make students clear rather than to teach more time. It's better for students to understand one idea using ten hours than be puzzled by ten ideas using one hour. Talking in class will make problems or notions more clear, which may not be rightly expressed and conveyed through rigid emails. Then why don't we adopt this method of encouraging students to speak out their doubts and ideas instead of compressing themselves to write a cold email? This is the appropriate way to approach more efficiency.
Efficiency is only one aspect to evaluate teaching results, and there is another important index--volume of knowledge students receive. Talking with teachers in class is immediate and direct to solve the problem at once, which will make it easier for you to understand the following lecture. However, if you intend to send your teacher an email after class, you will have to accumulate a number of unsolved questions which will make it harder and harder to understand other contents. So what you've learned is much less encountering so many obstacles.
In addition, communicating with teachers in the class will bring other benefits. This will practice your ability of discussing with others which is very important in modern society. What's more, having an equal communication with your teacher will offer you more confidence, thus greatly paves your way to future success.
In summary, communicating with teachers in class perfectly accords to the two main standards of evaluating teaching quality, that is efficiency and the knowledge volume student receive. As a consequence, I strongly recommend this way in teaching, which is just like a compass, directing us to sail safely on the stormy sea.