Mum of one Jane Barlow, 36, from Staffordshire, suffers from a side-effect of the sleep disorder narcolepsy, called cataplexy. It is trigged by embarrassment, shock and even laughter.
The sudden emotions can cause her to fall on the floor, and make her chest muscles collapse, leaving her unable to move, see or speak - so she must keep her emotions in check when teaching her pupils, however much they might wind her up!
Narcolepsy is an auto-immune disorder. It causes extreme drowsiness and sufferers to suddenly fall asleep for short bursts at any point in the day.
Over the years, Jane has managed to control the attacks, and teaches teenagers food technology at a high school in Newcastle.
"I use different methods now, like tapping my foot so I have something else to concentrate on, because if I concentrate really hard on something else I can stop myself from collapsing," says Jane.
I have learnt to suppress my emotions and have never collapsed at this school. Luckily, the one time I collapsed in class a while ago I was sitting on my desk so when I fell back the pupils just thought I was laughing.
"If I know I'm going to be watching something funny, like Peter Kay, I have to lie down on the floor but that means it takes ages to watch anything funny because I always have to stop and start it.
"I knew that I always wanted to have a career and I love my job. I was told before I was first diagnosed with narcolepsy that I would not pass my GCSEs or my A-levels and I was told this again with my teaching degree.
"I'm glad that I didn't let that stop me and I have proved them all wrong. Young sufferers should realise that you can succeed and achieve things in life."
Jane is mum to three-year-old Thomas, but her husband Carl has to take a very active role in the family home because of Jane's condition.
"At first it was really hard to get my head around not being able to do everything with Thomas that I wanted to," says Jane.
"It's hard to know that at the weekend when other mums are out playing with their children that I'm in bed sleeping. In the evenings I have to be in bed sometime between 7.30pm and 8.30pm because the narcolepsy means I have a really disturbed night's sleep, and can sometimes wake up 30 times a night.
"Luckily I've never seriously hurt myself in one of the falls. Once when I was pregnant I collapsed when I was walking upstairs, but luckily my husband was there to catch me
I collapsed once when I was getting a hot plate out of the oven because I just wasn't prepared for the shock of the heat. At home I try not to suppress my emotions as it can be become very depressing if you never laugh or express your feelings.
John Cherry, Chief Executive of Narcolepsy UK said: "It is only in the last 20 years that clinicians have started to understand what narcolepsy really is. When diagnosed at an early age, narcolepsy can be well controlled and the individual can go on to lead a near normal, productive life.
"While there is no cure for narcolepsy, several medication regimes combined with good sleep techniques can provide a great deal of relief for people with narcolepsy."