Moving from 6.5 to 7 depends on repairing the bottleneck.

Common mistake

Treating all four criteria evenly diffuses repair and leaves the main blocker unchanged.

Diagnostic evidence

If every feedback mentions the same issue type, that is the priority revision target.

What to confirm before writing

Put the main blockers from the last three essays side by side.

What to revise in the next version

Choose the most frequent criterion and verify evidence change with same-prompt revision.

• Whether the main blocker repeats
• Whether repair is focused
• Whether revision shows change

Four typical profiles stuck at 6.5

Profile one (most common): language largely clean, but every argument is claim plus example with no mechanism sentence — TR 6 drags the average. Profile two: full arguments but in-paragraph jumps, patched with Firstly/Moreover — CC 6. Profile three: ambitious vocabulary with high collocation error rate, not enough precision — LR 6. Profile four: error-free simple sentences, but clauses fail more often than not — GRA 6. Each profile needs a different repair, which is why "write ten more essays" usually fails: without knowing your profile, practice just reinforces the existing habit.

Worked example: repairing a 6.5 development chain to 7

Original: "Public parks improve mental health. Many studies show this. Therefore cities should build more parks." The problem is not grammar — there is no mechanism between assertion and conclusion. Repaired: "Public parks improve mental health because they offer the only no-cost space where city residents can exercise and meet neighbours daily. Regular users report lower stress in most urban surveys. Given that a single park serves thousands of nearby residents, expanding them is among the cheapest public-health tools a city has." One repair move only: after the claim, answer why it holds and through what path. This is the highest-frequency single fix from 6.5 to 7.

Why volume practice stops working at this band

Before 5.5, volume genuinely raises scores because the bottleneck is fluency. Past 6.5, the bottleneck becomes one or two specific habits: missing mechanism sentences, one recurring clause error, incomplete position coverage. Undiagnosed repetition makes those habits more fluent. The loop that works at this band: identify your profile, repair that single point, verify with a same-prompt rewrite, and only move to a new prompt after the evidence shows change.

• Diagnose the profile before choosing what to practise
• Repair one blocker at a time
• Same-prompt rewrite comparison, not gut feeling

The real cost and timeline of half a band

Moving 6.5 to 7 usually does not require improving everything — it requires lifting one criterion from 6 to 7. With the loop above, one blocker typically takes 2–4 same-prompt rewrite rounds: two to three weeks of targeted work, not another three months of prompt grinding. The risk is direction: repair the wrong blocker (profile one memorising a word list, say) and the time is fully wasted. That is why diagnosis precedes practice.