Bodily fluids, and the projection thereof, no longer send you gagging to the nearest loo.
You try to instruct greengrocers on the use of the apostrophe.
You're in on a Saturday night and you're on the TES forums.
You push and shove everyone into a straight line at Tesco's checkout.
"So long as you don't wake me up" feels like a perfectly reasonable response to a sexual advance a week before the end of term.
You get called 'Mum' for the first time by a 15-year old who couldn't possibly be be yours .
You being to set your family targets - a maximum of one major argument per month, working towards sitting down to a meal together three times a week.
You hear "Miss, miss" as you're walking through Asda on a Saturday afternoon and know the whole class will know exactly what was in your trolley by Monday 10am.
You tell people your job before your name...and hate yourself for it.
You get either chalk-infested sinuses, or a strange bruise on the heel of your hand caused by whiteboards.
You can't look at an adult without thinking, "I know exactly what you were like when you were nine."
And you can't look at a nine-year-old without thinking: "I know exactly what you'll be like when you're an adult."
You can only smoke in the privacy of your own home in case you see any of your pupils, pupils' parents or family.
You refer to people who are not related to you as "my kids" or "one of our parents".
You know you're a real teacher when you can tell a student, "I used to teach your dad."