The class system in Britian is rigid and social mobility is almost non-existant. However - forcing employers to hire kids from state schools is a terrible idea. There is a reason nobody wants to hire kids from state schools: they are disaster zones. If Britain was serious about tackling some of its current social problems there would be a massive overhaul of the education system. Teachers would be required to have some semi-decent qualifications, there would be rules that were actually enforced, the curriculum wouldn't read like watered-down daycare activities, kids would learn the real meaning of personal responsibility, they would not get stickers and points just for showing up to school and doing what is expected of normal well behaved children and then spend Friday afternoons singing ZippidyDooDa in the school gym after some fake awards ceremony to make them feel "special" (yes that really happens - I've seen it with my own eyes).
Instead, the solution of the British government is to try and force businesses to hire underqualified workers - a move that will surely perpetuate the incompetence that is rampant in today's Britain.