Till about pre-teen or so, it really isn't the child but the parent. Of course, even then if your parents never taught you how to behave, it is unlikely you are going to figure it all out on your own.
While teachers need to be held accountable for performance, you also have to have sympathy for them. They have the child for only 6 to 7 hours on 180 days a year. The rest of the time, it is the parents. Also, they don't see a child until he/she is 5 at the youngest. Plenty of time to have already learned lots of bad behavior.
And, if the teacher calls the parent about the child's behavior in school, guess who gets blamed and chewed out?