As a teacher, what are some dead giveaways that a student is going to be difficult to teach?

Violence, throwing ojects around the classroom, stealing and using extremely filthy language are dead giveaways. If such is ignored by school management and / parents as problems, then any chances of reform and meaningful education are highly unlikely. 

The students differ in their duties, but our generation has benefited from the heavy duties and the repetition of many writing exams , Additional duties also vary from student to student

I have NO idea what dead giveaway is, but I can tell there are difficult students. always, and yes, it is a hard toiling labor teaching them. Sometimes, the only motivating force for them to try any effort is a prospective of forthcoming exams