Oh dear, I've just read the Ofsted report:
"From discussions with leaders and governors and the examination of internal documentation, the decision to defer entry of Year 11 pupils to examinations for a year seems to have been driven at least as much by organisational concerns as by a consideration of individuals pupils’ educational needs. Specifically, the delay in the availability of the sixth-form provision until the school’s new building is completed in time for the academic year 2018/19 appears to have played a significant part in the decision-making process. In addition, when challenged as to why some pupils (for example, the most able) could not take some of the examinations at the usual time, leaders cited the perceived difficulties of teaching in small groups rather than justifying it in terms of the educational best interests of the pupils concerned."
And "In relation to the current Year 11, school leaders themselves judge that pupils have made such inadequate progress that they believe they would have significantly underachieved had they been entered for public examinations at the end of key stage 4. As a cohort, however, these pupils had average attainment at the end of key stage 2 that was higher than the national figure. This is an indication that teaching has failed to promote sufficient progress for these pupils. The work of pupils in Year 11 confirms this. It is also clear, however, that there are individual pupils who could have succeeded in public examinations had they been entered at the usual time."
So there were kids who should have been entered for GCSEs but they were held back because the school sixth form wasn't ready.
This isn't a special school or a PRU, it's just a catastrophically badly run one 