Reports and complaints

My children had their Open House meeting at school last week (a day to collect report cards and meet the respective subject teachers and class teachers). Every time I attend an Open House meeting, I wonder what the parents have to complain about to the teacher, that they take up more than half an hour of the teacher's time. Though the children are allotted a specific time slot to meet the teacher, never does the parent who is ahead of you keeps up the time. The parents talk, talk and talk endlessly with the class teacher. I am always at a loss when it comes to talking to the teacher- I simply cannot find things to talk or complain about. Usually, I am out within seconds after collecting the report card. It's not that my children are such perfect or wonderful students, that I don't have anything to complain about; it's just the feeling that if, as a parent, I cannot control two children at home, I have no right to expect the teacher to control what my child does within the few hours she spends with them. The teachers are, I feel, stressed out enough with having to handle hundreds of children everyday, keep teaching, organizing school activities, correcting test papers and assignment note books and still answer to the parents who come up with complaints such as "My child doesn't finish his/her lunch", "My son has lost two marks in maths class test and it was not even a valid mistake", "My child loses his/her pencil box once in two days"etc.
I personally feel that parents should learn to respect a teacher's profession and not regale them with silly complaints and harass them.
The best way to make these parents realize that the teachers have enough on their plate without extra helpings from them, is to force them to handle at least one session in a year for these children and experience firsthand what the teachers undergo every day of the year. I am sure that then, these Open House meetings would cease to be Complaint meetings!