In my point of view we should encourage them for every thing even though if they are doing wrong we should not criticize them but you know what's right and what's wrong you need to change your way to forbid that act such as if your student is not drawing well constantly but you are telling him or her its a good way to drawing a picture but she/he is not bothering you so, that time you have to thinks that what is best for them you should politely sit with them and take them in your confidence and you should say to her or him you are doing great job really i am appreciate you but if you do it seems like this or like that than its be a great for you.