When I had trainee teachers in my classroom I used to say to them, there will always be one, maybe two students you don't take to. Your job is to find the positives in them, and remember, they are the children of parents who love them. If you don;t find things to praise them for, you will be short-changing the child and the parents.

Interestingly they all worked hard to see positives in these students.

Still, we say, make sure you make a good impression.