For ambitious teachers who love being in the classroom, becoming an AST is the perfect move. It's a chance to develop your skills and take on responsibilities - without the desk duties that come with being head or deputy.
Then there's the money. Not all ASTs earn the top-bracket salary of Pounds 55,000, but the rewards are certainly attractive. You can usually count on an extra Pounds 5,000 to Pounds 10,000 on your salary, and the average pay for ASTs works out at around Pounds 40-45,000.
So what do you give in return? It goes without saying that you're expected to lead the way in your own school by delivering consistently excellent lessons. Most ASTs also spend one day a week doing outreach work. "I support teachers in other schools, develop resources and help to deliver CPD," says Pauline Hannigan, a primary science and design technology specialist in Cornwall.
"Outreach is one of the best things about being an AST. It gives you variety, and it's nice to work with adults as well as children." The only ASTs who don't do outreach work are those working in schools that are in special measures."
It's a common assumption that to become an AST you have to be an experienced teacher or head of department, but actually you can apply at any stage of your career. Some teachers have been appointed after just three years in the profession, and a quarter of ASTs are under 30.
At the other end of the scale, there have been cases of heads and deputies "stepping down" to finish their careers in the classroom. If you work part-time, you can still become an AST, with the amount of outreach work calculated as a proportion of your overall hours.
The whole accreditation process is a little complicated. You can't apply unless you have a specific job in mind. Some AST posts are advertised externally, others are created internally. Assuming you get accredited, you can take up an AST post if you're offered it, and you're also able to put yourself forward for other AST jobs in the future. If things don't go so well and your accreditation is refused, then you can reapply a few terms down the line, once you've addressed any shortcomings.
Martin Flatman, project director VT Education and Skills, which assesses ASTs through its National Assessment Agency, says that once you've downloaded an application form and answered all the questions, your headteacher needs to endorse the application. Then the National Assessment Agency will arrange for an assessor to come to your school, who will carry out interviews and observations to check whether you meet the relevant standards. The assessment day is rigorous but is a vital part of your professional development, according to Mr Flatman.
Noel Jenkins is an AST at Court Fields Community School in Somerset. He was running a geography department in an 11-18 inner-London school and finding it difficult to balance a full teaching timetable with an increasing number of curriculum development projects when he saw an AST role advertised. Now Mr Jenkins has one day a week off-timetable, which allows him to create and share ideas and resources more effectively.
"Typically, I might visit a school in some kind of advisory capacity or lead an Inset course. Or I might spend time developing a new resource. It's nice to have some time to reflect, on education and the reform agenda. Having said that, I always find that AST-related work takes up a lot more time than the allocated day," he says.
The internet is crucial to his work. Mr Jenkins publishes resources on his website www.juicygeography.co.uk and edits a blog on www.digitalgeography.co.uk. He's also experimenting with Twitter to develop his network. "In my spare time I write for a publisher, and do occasional consultancy work for the BBC," he adds.
"While I miss being a department head, there's no doubt that the AST role is the ideal job for me.
"I have no ambition whatsoever to become a deputy or head. The classroom is the only environment in which I feel truly comfortable."
- Next week: How to become a special educational needs co-ordinator (Senco).
WHAT YOU CAN EXPECT
- Salary Pounds 35,794 to Pounds 54,417 nationally. Up to Pounds 61,188 in inner London. It's an 18-point pay scale and you'll be appointed within a five-point range, moving up each September.
- Key qualities Detailed subject knowledge, excellent teaching skills.
- Next step See how you measure up against the assessment criteria at www.teachernet.gov.ukprofessionaldevelopmentast.