Since she was a little girl, Jo Wendholt dreamed of becoming a teacher.

She sat GCSEs and A levels and slaved away in clothes shops and banks to put herself through a four-year teaching degree at Brighton University.

Now, a few weeks before graduating, she is facing the prospect of being banned from state classrooms for life after failing a new maths test introduced last year by the Government.

Miss Wendholt, 22, from Horley, has failed the exam three times and has just one more chance.

She is one of many student teachers in Sussex and across Britain who are considering leaving the profession since the numeracy tests, described as "ludicrous" by education leaders, were introduced.

At Brighton University, a survey of trainee teachers showed the failure rate has leapt from three to 27 per cent in the past year.

Miss Wendholt is now planning to go abroad to teach English. She is so demoralised with the system she is not sure whether to sit the numeracy test for the fourth time.

One problem is students now have to sit the tests on a computer rather than writing answers on paper like last year.

Brighton University said students had reported their terminals were crashing, they were having difficulties registering for the exams, set by the Teacher Training Agency, and they had received little support from it.

Miss Wendholt, who specialises in teaching religious eduction, had to answer 12 mental arithmetic questions on headphones in 18 seconds and 28 questions in 45 minutes. She said during the exams, at Sussex University, students were wandering in and out, she could not hear the questions and her screen froze several times.

She said: "It is not that I can't do maths but the questions are really ambiguous and it is a really alien concept trying to answer questions on a PC. It is horrendous - four shots and you are out.

"I am a really strong teacher and I agree with the Government trying to raise numeracy standards. I would never have done a four-year degree if I had known at the end it would come down to this numeracy test."

Miss Wendholt passed all her dissertations with top marks and was given a good report from an Ofsted inspector for her maths teaching during a school placement.

She added: "I am not putting myself under the pressure of doing it again.

"I am completely demoralised and I feel like I am a failure when that is not at all the case. I always wanted to be a teacher and I know I am good at it."

She will qualify with a BA Hons in education, allowing her to teach in private schools but will not get qualified teacher status.

Diana Brightling, co-ordinator in student teacher education at Brighton University, described the numeracy test system as "ludicrous". She said a student who had been offered a job at a school had also failed the test three times and a graduate, who had been working at a Brighton school for a year, could lose her job.

Ms Brightling said: "None of the students knew the Government was going to be putting this hurdle in front of them in the final stages and assess them in this inappropriate and inhumane way. For students like Jo, the pressure before they even sit in front on the computer is enormous.

"The tragic thing is, Jo is an extremely strong teacher. I have been saying from the beginning this system is misguided and there would be lots of casualties but I did not realise just how many there would be.

"It is also a tragedy for the country at a time when we are desperate for good qualified teachers."

A spokesman for the Department of Education said trainees could always try to do their entire degree or teacher training again, if they could find someone to accept them.

He said: "We make no apology for ensuring that newly qualified teachers have the necessary numeracy skills to carry out their jobs effectively.

Evidence from Ofsted has confirmed that the numeracy standards for a significant number of teachers in schools are not good enough. Newly qualified teachers get four chances to pass it.

We recognise that for those individuals who fail four times it will be a considerable blow. However, in order to raise standards in schools it is necessary for NQTs to have these skills."