Chicago ? A sense of order and decorum prevails at Noble Street College Prep as students move quickly through a hallway adorned with banners from dozens of colleges. Everyone wears a school polo shirt neatly tucked into khaki trousers. There’s plenty of chatter but no jostling, no cellphones and no dawdling.

The reason, administrators say, is that students have learned there is a price to pay — literally — for breaking even the smallest rules.

Noble Network of Charter Schools charges students at its 10 Chicago high schools $5 for detentions stemming from infractions that include chewing gum and having untied shoelaces. Last school year it collected almost $190,000 in discipline “fees” from detentions and behavior classes — a policy drawing fire from some parents, advocacy groups and education experts.

Officials at the rapidly expanding network, heralded by Mayor Rahm Emanuel as a model for the city, say the fees offset the cost of running the detention program and help keep small problems from becoming big ones. Critics say Noble is nickel-and-diming its mostly low-income students over insignificant, made-up infractions that force out kids administrators don’t want.

“We think this just goes over the line … fining someone for having their shoelaces untied (or) a button unbuttoned goes to harassment, not discipline,” said Julie Woestehoff, executive director of the Chicago advocacy group Parents United for Responsible Education, which staged protests last week over the policy after Woestehoff said she was approached by an upset parent.

Students at Noble schools receive demerits for various infractions — four for having a cellphone or one for untied shoelaces. Four demerits within a two-week period earn them a detention and $5 fine. Students who get 12 detentions in a year must attend a summer behavior class that costs $140.

Superintendent Michael Milkie said the policy teaches the kids — overwhelmingly poor, minority and often hoping to be the first in their families to attend college — to follow rules and produces a structured learning environment. He points to the network’s average ACT score of 20.3, which is higher than at the city’s other non-selective public schools, and says more than 90 percent of Noble graduates enroll in college.