Harsh or No?

The kids school has a rule implemented, mainly for the third grades and up, that if the students don't complete their homework or misbehave enough times they get a check mark against them. Three check marks will earn them an after school detention (ASD) for an hour where they can not speak during that time and are given a homework packet by their teacher to complete. These marks are reset at the end of each nine week period so if they have two checks at the end of the term, then they get a clean slate next nine weeks. Bryce has had four check marks over the last three weeks because he has forgotten to bring his homework home resulting in his first ASD for this year. He had one at the end of fourth grade and one in third. Hubby believes that it isn't right for the school to impose this rule at this level, that the check marks should be restarted at the end of each week and not every nine weeks. I say that the kids are very much aware of this rule as are the parents - the parents sign forms explaining the rule each year - and if they choose not to do their homework or take the time to remember to pack their homework then they should pay. This is the schools way of ensuring the kids realize that behaving and completing homework is an important part of growing up and ensures they become more responsible as they grow older. Am I wrong in believing the kids should be punished for not completing homework on a nine week basis?