Schools are 'off-rolling' poorly-performing pupils to protect their academic profile despite the practice being prohibited.
The Centre for Social Justice believes a spike in exclusions during January 2023 is due to schools deliberately dumping those likely to do badly in their GCSEs.
They were taken off the register just before the date at which their grades would count in official league tables.
Many of these students, who may simply be struggling academically, end up in 'pupil referral units' (PRUs) with badly behaved children.
But others can be taken in by other schools or taught at home, despite warnings about it first emanating in 2018.
According to the CBJ, a centre-right think-tank, the number of Year 11 pupils in PRUs rose by 488 in January 2023, compared to a net increase of 395 the previous term.
The rise in the number of Year 11s entering the PRUs in January 2023 was bigger than in any other term across every other age group.
This evidence comes despite school inspectorate Ofsted ruling the practice can be 'unlawful' and is in all cases 'never acceptable'.
Schools are meant to expel pupils only as a last resort and that 'academic attainment/ability' is not a valid reason to expel a pupil.
Andy Cook, CSJ chief executive, told the Sunday Times: 'Our reports today support what many parents who work with our front-line charities have been saying for years, namely the practice of schools dumping kids in Year 11 to sustain their performance data.
'A system which effectively rewards schools for exiting academically underperforming students is not acceptable.
