Top 20 constituencies in England and Wales with adults aged 16+ with no qualifications, according to the 2021 Census. The overall percentage is 18.2%:

Leicester East, East Midlands - 32.8%
Birmingham Hodge Hill, West Midlands - 32.8%
West Bromwich West, West Midlands - 30.1%
Clacton, East of England - 29.8%
Walsall North, West Midlands - 29.4%
Wolverhampton South East, West Midlands - 29.3%
Bradford West, Yorkshire and The Humber - 29%
Bradford East, Yorkshire and The Humber - 28.9%
West Bromwich East, West Midlands - 28.8%
Boston and Skegness, East Midlands - 28.7%
Warley, West Midlands - 28.6%
Sheffield Brightside and Hillsborough, Yorkshire and The Humber - 28.5%
Rhondda, Wales - 28.2%
Liverpool Walton, Northwest England - 28.2%
Merthyr Tydfil and Rhymney, Wales - 28%
Blaenau Gwent, Wales - 27.9%
Rotherham, Yorkshire and The Humber - 27.5%
Knowsley, Northwest England - 27.5%
Edmonton, Outer London - 27.3%
Birmingham Erdington, West Midlands - 27.1%