Teachers, as has already been pointed out, do get PRP.
Parents are able to refer their own child to the SENCo if they believe their child has additional needs.
I would take issue with your claim that 'many mainstream schools ignore many SEN children'...really? You have actual evidence of this as opposed to many mainstream schools have insufficient resources/training to adequately and appropriately support children with SEN.
I have a Y4 class in a mainstream school. They range from being completely unable to read and write to performing maths at the level expected of a pupil in Y7/8. For an hour a day I have an additional adult to support me/the children. I have asked and asked and asked for specific interventions, referrals and assessments but I can't get what the LA don't offer.
Please don't beat up the teachers. If you believe your child's needs are not being met in a mainstream setting then you need to make waves in your child's school. Put your requests/concerns in writing to the SENCo, Head and Governor with responsibility for SEN. Copy these to the Director of Children's Services, use the expertise of organisations such as IPSEA. But please, don't jump to the conclusion that because a single, mainstream teacher (who may well have received little or no training in specific SEN issues) has upset you, we are all like that or that our pay isn't already linked to the performance of the children we teach
.