Some people say that language teacher should concentrate on giving positive feedbacks to student when they do good work rather than on criticising bad work but other people say this bad things. Positive feedbacks give student encourage and make thetll have a nice day. When you positive feedbacks, you want to study more learn fast. Criticise is easy but does it really make student good. But other peoples say, cannot have easy life every day, have to critic sometime. So it complicate subjects and many different opinion we must discuss it.
The advantage is that when he tell student your work is very good. you learn English the best way and very good. Every student want to hear his work is better than other student. In my school in my own country, every boy and girl want teacher tell is good. Then next day they work more hard and next day more hard is best way but if teacher you work is no good you lazy boy they no like English and they want stay home or study math. Make encourage is most important things and give positive feedbacks most important things.
The disadvantage that in your life is sometimes you criticising how can you improve your English when you never criticising. Have to know bad point as well as good point or is no way a good way to learn. When your english bad teacher have to tell your english bad or you say same bad things again and again. Knowing your mistake is that teacher tell you watch your mouth then you can improve your english is good way.
For conclude is advantage and disadvantage and every teacher must decide hiself if he do positive feedbacks or criticising your english because you can have both but must choose best way for student.