Students' Contribution to the School Canteen

A school mentions that it takes money from the female students and places it in the school box with the intention that it is a contribution to the canteen, but the money does not move from the box throughout the year. At the end of the year, they take out the money; for example, if a student paid ten riyals, they give her (25) according to the contributions in the school, but this money does not come out of the box. Is there any harm in that?
There is no harm in this; because these coins that are placed in the box are considered a deposit, and the teachers lend the students what they spend on this canteen. So if at the end of the year they calculate the expenditure and the profit, and then return it to the students.