Sometimes the blackboard jungle seems too much and those light-bulb moments when pupils respond too few. Paperwork, marking and the non-stop need to stay on top of behaviour and achievement can drag you down.
According to the Conservatives, 100,000 teachers voted with their feet and left the profession between 2000 and 2005. "I actually fell asleep on my feet in the classroom," says Charlotte Brown (not her real name). "I was green in the face and a colleague had to take me home."
Yet if you want out of the classroom and still feel committed to education, what are the options? Despite the recession, it may be a good time to find a non-classroom job.
Key government initiatives are run by private companies who need education employees: the delivery of the National Strategies for the curriculum, Building Schools for the Future (BSF), leadership programmes and continuing professional development (CPD). Many firms look for teachers, valuing their transferable skills.
Capita, for instance, runs the National Strategies, overseeing the delivery of the national curriculum; Atkins, the major transport and services company, runs several academies; VT, a huge conglomerate, includes the National Assessment Agency for Advanced Skills Teachers (ASTs) and Excellent Teachers (ETs) in its education and skills division.
Martin Flatman works as director of the AST and ET programmes for VT Education and Skills. He says he loves schools and spends a day a week helping assess excellence in teaching. Having taught music and RE for 17 years up to assistant head level, his first move into management in a local authority vocational programme was dictated by salary, he says. Latterly, though, his career progress has been led by the sense that "I can do this. It's challenging and I can make a difference."
He says: "That flexibility and determination needed in a classroom are the best transferable skills: knowing that there are many ways to reach a goal, that there is always an alternative that's worth exploring."
As BSF rolls out over the next 15 years, it will create opportunities in local authorities and in giant building firms, such as Taylor Woodrow, ICT companies such as Civica or RM, and educational management firms such as Nord Anglia or Serco.
A typical job advertisement for an educational consultant on a BSF project asks for people who "have a good understanding of the education sector and the challenges it now faces".
Dave Williamson works in the London borough of Haringey as head of innovation, responsible for the educational direction of capital investments, such as this year's Pounds 24 million investment in secondary ICT and a Pounds 160m BSF programme.
Dave agrees that teamwork and determination pay off in educational management, but stresses the value of experience. "It's my knowledge of how schools work that means I know how to help architects and designers shape the buildings we need to transform education," he says.
The most traditional route out of the classroom remains local authorities, whose children's services are mostly staffed by ex-teachers. For Charlotte Brown, a secondary English teacher for 12 years, moving to the advisory service was a gamble, taken because of the pressures of rapid promotion without adequate support, a young family and a head she claimed was a bully. The work-life balance, she says, had become unbearable.
Five years later, she loves her job, works with a great team, can arrange flexible hours and has no more marking - "I hated the marking," she says. But she is paid less than the people she supports.
Dave Williamson confirms this. "If I'd stayed and become a headteacher, which was the other option, I'd say over the years I'd be Pounds 300,000 better off. But I've got a better quality of life."
Starting off as an art teacher, then head of department, Dave was head of secondary standards in Haringey and observes: "People say that those who work in an advisory capacity can't teach, but that's not true. If you've got no credibility as a teacher, you can't work in a local authority: teachers won't listen to you or believe in you."
Dave knows many people who have gone from the classroom into museums, arts organisations, exam boards, the civil service, recruitment agencies, the media, educational suppliers and publishers. He says: "Of all skills, communication is central."
"Teachers have to be good communicators, able to pick up on learners' needs and assess situations quickly: all skills needed in business," says Romey Tacon, who runs Numicon (www.numicon.com), which sells maths materials and teacher training for key stages 1 and 2.
Romey worked as teacher and headteacher for 22 years, before bureaucracy "nearly finished me off. I believe that creativity is what is important - and what works - in teaching. I still go into schools, but on a voluntary basis. I use my creativity daily and I see children and teachers beam when they realise that maths is fun."
Jo Peat has a similar story, but went into higher education instead of business. She taught French and German for 15 years, to all ages, but was "fed up with kowtowing to a national curriculum that was led by external assessment".
Despite earning significantly less at Roehampton University than in school, Jo feels that she has rediscovered the creativity and teacher autonomy disappearing in schools. Nonetheless, she volunteers in schools in her spare time.
Her colleague at Roehampton, Carrie Winstanley, a principal lecturer, has won Pounds 10,000 to be used for personal development in learning and teaching as one of this year's 50 National Teaching Fellowship awards.
She puts her own successful academic career - as an educational researcher and university course leader - down to a decade of special needs teaching in schools, at home and abroad and continuing involvement in education.
"Hankering for children in a classroom", she runs family workshops in museums and galleries, as well as supervising pupils.
Classroom skills of planning for different learners' needs remain crucial in her work, as does the empathy she developed working with special needs. "Understanding more about how people are is thrilling work," she says.
Opportunities to research into "how people are" abound in organisations such as the Qualifications and Curriculum Authority (QCA) and Ofsted.
The NCSL (National College for School Leadership) set up in 2000, was joined by the TDA (Training and Development Agency for schools) and the NCETM (National Centre for Excellence in the Teaching of Mathematics) in 2005; this autumn, the Learning and Skills Improvement Service (LSIS) formed to develop FE provision.
Philippa Cordingley at the Centre for the Use of Research and Evidence in Education (CUREE) says: "We always have three or four recent teachers on our staff keen to move beyond the pressures of the classroom and think more deeply about things."
Researchers often return to schools. Tim Stirrup speaks for many when he says: "My instincts for teaching remain and the urge to return to teaching in the classroom resurfaces regularly. I don't think I would ever rule out a return to the classroom. Whether schools would want me is another question."
And, of course, it could go the other way: Sara Morgan, a teacher of 25 years now runs the Teacher Learning Academy at England's General Teaching Council as head of professional learning (www.gtce.org.uktla).
She says: "If you have never been a teacher and are considering it as a sideways move from another career, my advice would be to go for it."
VOICE OF EXPERIENCE
Tim Stirrup was a secondary maths teacher for 10 years, with breaks to run his own sportswear business and work as national contract manager for an educational supplies company, where he took an MBA. He moved back from commerce to the London Grid for Learning and has just taken up a post as communications director for the National Centre for Excellence in the Teaching of Mathematics (NCETM).
"I don't think of myself as `giving up' teaching," he says. "Yes, in the commercial sector the financial rewards provided as my young family grew were much greater than I had as a teacher, or have now (with NCETM). But with reward comes risk. The Pounds 80k salary can be taken away rather quickly, something all too obvious this month."
He points to teachers' valuable strengths in building relationships under pressure. "Good relationships result in good business and better service delivery. Business people appreciate your ability to reach decisions quickly, which comes from years of thinking on your feet."
Do's and don'ts
Do: research carefully. Weigh up holidays, time commitments, satisfactions, salary and status: what is more important to you?
Don't: play your skills down.
Don't: make a move in a hurry. It is not easy to go back in the classroom again after a few years, especially if you are senior.