The national schools commissioner wants to challenge the idea there are only “the very best” or “very weak” schools by identifying them along eight different streams: strongest performers, rapid improvers, steady improvers, steady and secure, rapid decliners, steady decliners, improver decliners, and weakest performers.

At a conference in London on Tuesday, Sir David Carter revealed his “Schematic” tool, which CEOs, RSCs and other school leaders can use to work out whether their school is improving or declining. It will also be provided as a paper package for multi-academy trust leaders during internal reviews.

Sir David believes the tool is “more subtle” than Ofsted judgments and will give leaders more information about steps they should take to increase their schools’ performance.

He wants it to challenge the idea that schools are either “the very best” or “very weak”. He believes instead that there are eight categories, ranging from the “strongest performers” whose performance remains excellent over time, and “rapid improvers” whose performance suddenly shoots up, to “steady improvers” whose performance gets better over a longer time, and the “steady and secure” which are quite good and don’t dip.

On the other side of the divide, he has identified “rapid decliners” whose performance drops drastically, “steady decliners” where performance tapers down over time, “improver decliners” which make initial gains but see a drop, and the “weakest performers” which rarely hit floor standards and see consistently poor results.

Schematic echoes the health-checks for multi-academy trusts that were piloted from January. It should allow leaders to gauge which schools and trusts are “capacity givers”, and so should expand, and which are “capacity takers” and should not.

Once a “capacity taker” is improving again, Sir David wants it to “repay its debt” and help other schools do the same, he told delegates at the Westminster Education Forum.

The model will be shared with schools as “widely as possible” between now and Christmas, although its use will not be compulsory.

He told Schools Week that RSCs may use the labels to “talk over” expansion plans with MATs, adding that the team had “quite deliberately” not recreated Ofsted grades but were instead going for a measure of improvement that was “more subtle”.

“School improvement is not linear, it’s messy,” he said.

But Robert Hill, an education consultant, said he “wasn’t sure another categorisation model is what schools need right now”.

His words were echoed by Mark Wright, director of AMiE, ATL’s leadership section of the National Education Union. He believes the tool could be “another trawl for evidence” which would add to headteachers’ workloads, and wants to know “exactly what kind of criteria” are behind each category.

Neither Progress 8 nor exam results are flawless measures, he pointed out.

However, Geoff Barton, the general secretary of the Association of School and College Leaders, said Sir David had put huge work into the model, and brought “a real intelligence” about the school system.

He welcomed its rejection of “gimmicky quick-hits” and emphasis on school improvement as evolutionary.