This may not apply, but nowadays for school lunches, the students all pay by plastic card (I'm not sure if it's a true debit card or if it's a card only good at the school cafeteria). Money is put "on the card" by the parents paying, or somebody paying into the student's account.
If your family is poor and you qualify for the reduced-price school lunch, the card reader "knows" that and deducts the appropriate amount from your account.
This is nice because no one can tell if you're a "poor student" or not. All the students pay with cards so there's no singling out. Back in the day, that was not the case, and everyone knew who was poor and who wasn't. (Which is tough when you're a teenager and you have such identity issues anyway.)
However, I don't think they had this technology in the 1980's, if you're going to set your fic at that time.
