I think it's better to use the word "retention", there are plenty of collages and sixth forms in the Mansfield area, but a lot of their alumni move away.So the educational attainment of the residents of Mansfield is way below what would be expected nationwide. That's not to say everyone in Mansfield has low educational attainment. But what I have said is, regrettably, true in aggregate.
The nearby Shirebrook Colliery is a good example of why, there used to be a mine, providing well paid (and admittedly difficult, and dangerous) jobs, with both options for managerial and technical progression for the locals. Now there is a big set of warehouses, providing minimum wage jobs with bad conditions, to a mostly immigrant workforce.