Not all parents are like this. There are definitely some, but you will get shit parents in all walks of life with all kinds of children.
The majority of SEN parents are just like any other parent and are supportive and open with school. But they have a whole heap of added pressure having a child(ren) with things like delayed learning and speech, delayed toilet training, sensory disorders, problems when over stimulated, meltdowns, social difficulties, eating problems, inability to concentrate the list is endless.
Sadly many people on this thread seem to think that parents of SEN children prone to violent behaviour are shit parents and don't care about anything or anyone else. That isn't true. But like any other parent they are putting their child's needs first and are often in an impossibly difficult position. A little bit of understanding goes a long way, you can fight for what is right for your own child without verbally battering parents who more than likely are already exhausted and are being told every way they turn that they or their child are doing something wrong.
Imagine having a child (with diagnosed SEN) prone to having violent outbursts in school. Imagine being told they don't meet the criteria for an more funding or a place in a special school. Imagine having to take them to mainstream every day knowing they need the funding to provide the supervision and support they need and it's been refused. Imagine other parents thinking they know best and saying they should be excluded or home schooled.
What do you do then. You can't afford not to work. You can't just drop everything to home school You have no way of moving them a special school because the local authority said no. School haven't got the money to pay for a 1-1 to cobble something together as best they can. Then an incident happens and it causes upset/harm for other children.
But you are a shit parent because the system is failing your child and you literally have nowhere to turn.
So what's the answer?