It should be based on the pass fail rate of the students. Like it was said previously, salesman can say "You can't make a customer buy" but the great salesman close the majority of the time.
Now as for a standard. Like it's stated above, figure out where the child is at academically and place them accordingly. Give them a good teacher who can make them progress and at the end of the EOCs for everyone. Teachers with unacceptable failure rates aren't doing their due diligence. I'm only 22 but I remember all the teachers who would help at the end of the day if you didn't understand a concept or needed so extra help.
It's like our teachers want to get paid, a pretty good wage I might add, and not really have to teach more than what is required by law. Take the law out of it, still fund the schools and the teachers, and require the parents to sign off on homework. Problem solved.