I don't think they could get any worse than they are now. My missus is a teacher and has taught in Bradford schools, they currently are all failing for the most part. All the teachers want out because of poor head teachers or terrible discipline. Discipline, needs to be managed on a whole school basis, or it quickly fails. At one school my missus taught at a teacher got her arm broken and there are various other assaults on teachers aside from swearing and abuse towards teachers. The teachers/behavioural management knew that the kids have an area where they sit around and smoke weed and never tackled the issue. Now in that school my missus says she basically couldn't teach a lesson plan half of the time because most of the time she's trying to police unruly kids, some of them off their head. In her current school, also in a disadvantaged area has good discipline, so she can actually teach.
Discipline needs to be managed on a whole school basis. There's behavioural management team that either drill the kids early with bollockings and punishes them or lets things slip. The only good school in a disadvantaged area she's taught are are well managed with year 7s from day one basically not letting them step an inch out of line. You can contrast this with our nearest school where a teacher where teachers say the pupils run the corridors.
When my missus left the poorly disciplined school, more than half of the teachers the school. They had to get in PE teachers to teach English. After she left she received an email from an A Level pupil begging for tutoring because the deputy head wasn't teaching, he continually left the class giving them book work and was found by said pupil in his office playing a computer game when he was supposed to be teaching.
Now I think all kids should have a good education but especially those who actually want to learn but in Bradford and the rest of the country there is no party with a policy to tackle these issues. Having more money will help but it won't help a school with poor discipline with poor management.
Part of the problem is kids who don't want to learn drag other kids down to their level. Kids and parents have some personal responsibility to aspire. That attitude of some to education is the polar opposite to what you'd see in Chinese schools or grammar schools. So yes children who want to learn should be separated from kids who don't want to learn that will pull them down. There's nothing elitist about that.