Kudos to the New York Post for revealing today that New York City’s ban on cellphones in schools is taking $4.2 million a year out of frequently impoverished childrens’ pockets.

The students — who attend the nearly 90 high schools and middle schools in the five boroughs with permanent metal detectors — pay $1 a day to store their phones either in stores or in trucks that park around the buildings. Down the block from The Nation offices on Irving Place, you can see long lines of kids each afternoon from nearby Washington Irving High School waiting to pick up their phones after school from an idling truck.

The cottage industry has become so profitable, it rakes in $22,800 a day from some of the city’s poorest youngsters, whose families choose to shell out the money rather than risk their children’s safety by putting them out of the range of easy communication.

Parents and students quoted by the Post said the robbery highlighted the Department of Education’s indifference to the plight of high-poverty families and Mayor Bloomberg’s unwillingness to compromise. ”He seems totally unconcerned with how his policies negatively affect students, and he seems totally scornful of the concerns of parents,” said Leonie Haimson, whose son is an eighth-grader at the School of the Future in Manhattan.

Students say schools that enforce the ban should offer more options. Bronx high schooler Jonathan Lauriano, 18, told the Post he’d spent $500 on cellphone storage at a truck near campus. “They should set up free lock boxes inside [the school] because we can’t all afford to pay a dollar a day," he said.   But, as the Huffington Post subsequently reported, the NYC Department of Education has opposed efforts to construct on-site storage facilities for students, arguing that the liability for schools storing thousands of phones and gadgets is too high.