The cases, which could open the floodgates to dozens of similar actions, follow an out-of-court settlement last month in which a 20-year-old accepted pounds 30,000 damages after claiming compensation for bullying at school.
However, head teachers believe it will be very difficult for the pupils, who say their education was so poor that they failed to get the GCSE grades they deserved, to prove their case. Teachers are also concerned that schools will have to spend money which is needed for pupils' education on insuring themselves against legal action.
Both cases have been made possible because of government policy which requires inspectors to say when schools are failing. Both schools are among 200 declared failing by the Office for Standards in Education.
The two former pupils have begun legal proceedings on the basis of inspectors' reports. They are a 17-year-old girl who left school two years ago with no GCSEs and a 17-year-old boy who got unexpectedly poor grades. Both say they were expected to do better.
They are now on GCSE courses at sixth-form colleges and are suing for the cost of retaking their exams and loss of earnings because they could not go straight into jobs.
David Hart, general secretary of the National Association of Head Teachers, said he thought the chance of a successful case being brought against a failing school was remote. There were so many factors other than the quality of teaching that caused pupils to fail to achieve GCSE grades: motivation, family circumstances and the role of parents.
A research study by Professor Peter Mortimore and Sally Thomas from London University's Institute of Education showed that schools make a difference to GCSE performance. The amount is relatively small but it could be as much as the difference between seven Bs and seven Ds.
But Professor Mortimore said: "Research has quite a lot to say about what happens at school level, but at an individual level I think it would be extraordinary difficult to allocate responsibility for GCSE performance."
Lawyers involved in the two cases believe that those pupils with most chance of success will be those who retake qualifications. Jack Rabinowicz told BBC Radio 4's The World This Weekend: "Here we are talking about pupils who should have done better and where the school has been labelled a failure. If you have a car where the brakes fail there are victims, similarly, if you have a school which fails its pupils, there are victims."
He said the pupils were undergoing tests from educational psychologists to try to demonstrate that they should have done better.
Doug McAvoy, general secretary of the National Union of Teachers, said many factors affecting schools performance - what they taught and the money they were given - were beyond their control. "It is a very worrying development, it could have a devastating effect, particularly on schools' finances."Reuse content