Too many students 'get by' and seek tactics that lead to good marks not good learning.
'Never praise a child, praise what they did' says Professor Black, and by this he meant praise the work of the learner and not the learner.
To praise the student encourages two ideas that are powerfully corrosive in learning; a) the idea that it's all down to ability b) the idea that the 'teacher' likes me.
To counter this, teachers must praise the work and effort, not ability of the student. Nor should teachers compare students with other students.
Praising the person also stops students from trying harder. Learners must believe they can change for the better.
Alfie Kohn offers another good reason for not praising children as he describes in this short video clip from one of his talks.