The GCSE changes announced today will not give schools what they most crave - stability.

But they will at least provide some idea of how they can weather the hurricane of exam, curriculum and accountability change that is about to rip through England’s secondary education system.

For at least four years, teachers will have to cope with two sets of exams - both called GCSEs - with their own separate standards and completely different grading systems, A*-G for the old and 9-1 for the new.

Today Ofqual revealed how schools will be able to compare them, with a grade 4 in the reformed GCSEs being phased in from next year, equating to a grade C in the legacy qualifications.

Some exam board insiders feel this bridge between the two could exert an unhelpful “gravitational pull” on the new qualifications, taking them away from higher standards they were supposed to herald.

But it should offer some relief for teachers who now have a reference point for what they will be expected to target.

And with six different grades pitched at “C” or above, compared with the current four there will still be plenty of scope for higher expectations.

If, as Ofqual proposes, the new grade 9 is reserved for “really exceptional” performances - secured by just half the number of the candidates that currently achieve an A* - then competition between schools that currently top the league tables can only intensify.

It should mean that even grammar schools benefiting from the highest-ability intakes will be unable to rest on their laurels.

All secondaries may find more comfort in the plan for a “national reference test”. It could provide an answer to increasingly indignant cries from teachers who want to know how their pupils’ improved standards can be recognised in an era where GCSE results are pegged to previous years performances.

Ofqual’s tougher application of its “comparable outcomes” approach has ended a long and steady annual increase in the proportion of pupils achieving good grades.

The regulator always said it would allow grades to rise if standards had genuinely improved. But it never really explained how schools or anyone else were expected to prove that.

The new reference test - to be sat by a representative sample of GCSE students every year in English and maths - could offer a solution.

Ofqual’s chief regulator, Glenys Stacey, said preparatory work had already started. “It is one more piece of evidence and it may provide the evidence that will support change in the proportion of students… that would achieve higher GCSE grades,” she said.

But some exam industry insiders are warning that too much emphasis is being placed on it and human judgment will still have to play a role.

Much of the attention this morning is likely to be focused on the new grade 5 - because Ofqual has portrayed it as the new “pass grade” and because it will be explicitly linked to standards in other “top-performing” systems.

The existing C “pass grade” has been crucial for schools because of its importance in government league table measures. A new school accountability system that awards points for all grades should mean that no single grade acquires the same massive significance.

It is the reaction of employers that is likely to determine whether it does become the “pass grade”.

But the proposed use of the Pisa (Programme for International Student Assessment) evidence to set it has already been criticised by both heads’ unions. And the idea that this benchmarking will be reviewed, even on “a periodic basis”, could play havoc with Ofqual’s duty to maintain exam standards from year to year.