Teachers have little money at home or in school, but bank managers have oodles of it. Schools are often crumbling, banks are luxuriant. Public versus private, principles versus profit, elbow patch versus three-piece suit.
The tension between bankers and pedagogues was confirmed by the unhappy experience of a teacher who applied for a credit card with a building society.
He was told he had ticked the wrong box on his application form. Eighteen-year-old students are offered a Donald Duck watch to open an account, but teachers are not even categorised as "professional" in this building society. They have to tick the box headed "other". He wrote back and told the toffee-noses where to put their strip of plastic.
It reminded me of when I first started teaching and wanted to borrow pound;100 to buy a 10-year-old Austin. The bank manager looked me up and down contemptuously, as only true snobs can, and said: "We don't lend money to teachers."
I felt like replying: "Well, we don't teach the children of dickheads", but did not, because it would have been undignified and untrue. The temptation to wipe one's nose on the velvet curtains, however, was overwhelming.
On another occasion, having drifted all of pound;10 into the red for three months in a row, I was invited to meet his deputy manager "to discuss your financial options", as he put it. The deputy was a perfect clone of the chief prat.
"I think it's clear what the problem is," the number 2 sage began. I perked up at the thought of having my funds sorted at a stroke. "We are living beyond our means," he went on. We? You might be, sunshine, I thought to myself, but I'm just plain skint.
Teachers ought to be an attractive proposition to a bank: salaried, straight, sober, law-abiding citizens. What more could anyone want? What banks would prefer, in a nutshell, is someone who earns a lot more loot.
Whereas schools are expected to be consistent in their policies and practice, banks can veer wildly from one year to the next. Some time after my bank manager refused to lend me pound;100, banks changed their policies completely.
Suddenly it was good to borrow and to be in debt.
Each visit to the bank saw my snobby friend transformed. Now he oiled around the counters, sidling up to unsuspecting customers: "Pssst. Want a washing machine or a new colour television?" I felt like dialling 999: "Get me the police. There's a maniac on the loose trying to ram tenners into people's pockets."
Nowadays, I meet some very pleasant bank managers, particularly those who are school governors, but these early experiences when you start teaching can leave deep scars. Unable to cope with the hypocrisy of banks, I have rarely been into one in the last 20 years. When they ran the advertising slogan "There's a bank manager in every cupboard" I kept my wardrobe locked, hoping mine would suffocate.
Perhaps the answer is to pretend to be better off than you are: "Oh yes, in my job I am responsible for an eight-figure budget" (pound;29.50 for books, pound;21.99 for equipment); or "You will recall that my friend Mr Major, when he was Prime Minister, said he wanted every teacher to have a new car standing in his drive" (but it was a Dinky car and you ran over it in your 1983 Skoda).
Your own finances could also offer useful source material and real-life data for the numeracy hour, particularly effective for teaching the normally difficult concept of "negative numbers".
Alternatively, try being assertive. If the bank manager turns unpleasant, threaten to take your account elsewhere. He will then get it in the neck for losing a customer.
How do you take a deficit to another bank? Nothing could be easier. You simply go in and say, "Give me pound;100, I want to open an overdraft".