Why is he not in school

[Jackanorystory1]

Cousin has an autistic (non verbal) son. He went to childcare 1 day a week whilst she worked and has now stopped. They mainly stay home each day.
Dad is not in the scene at all. They live in a high rise so have no garden. DS will be 5 in March and he has not yet started school so has no friends and no one to play with. She doesn't take him to any groups so he is with her all day every day.
6 months ago she had another baby. DD from the same man as DS1.
DS1 has not yet started school and when I asked her why she claimed that he didn't have a place. Now I'm under the impression that all children receive a school place.
This must be harming the child by keeping him at home all day and not mixing.
Is it not against the law to keep your child at home.
I really do not know what to do. I would like to ask her what is going on but she tends to fly off the handle so quickly. Aibu to think that this is harming her child.

The plan is sent to the schools and they can say they are unable to meet the child's needs and not accept him. Special schools are full so many are waiting around for a space.

Not quite. Unless the school is wholly independent, the LA must name the parent’s preferred school unless the LA can prove:
-The setting is unsuitable for the age, ability, aptitude or special educational needs (“SEN”) of the child or young person; or
-The attendance of the child or young person would be incompatible with the provision of efficient education for others; or
-The attendance of the child or young person would be incompatible with the efficient use of resources.

When consulted, schools can object, but unless they are wholly independent, they can, and must unless one of the above can be proven, be named even if they object. If the school is named in the EHCP, they must admit and can be forced to via judicial review if they try not to.

Being full is not defined in law, and on its own being ‘full’ is not enough of a reason to refuse to name the parental preference. The LA has to prove the school is so full admitting DC is incompatible. Which is a higher bar than many LAs and schools admit.

Although this doesn’t stop LAs from trying to refuse and forcing parents to appeal.

id be more worried about them never going out than school cant be any good for their health

Well yes I do think this would be sensible to investigate the reason why, but there are a lot of times where DS and I don't surface for a while because we are both autistic and we have everything that makes us happy and comfortable at home.

I only have 1 child, but if I had 2 I'd place more effort into making sure the one that could become thrown off by changes to the environment was regulated as it would make meeting both childrens needs easier.

Obviously I don't know if that's the reason why this woman doesn't take her children out, equally nor do I know if OP is using the word never as hyperbole for infrequently or whether she genuinely feels that there are some legitimate safeguarding concerns that need to be addressed. If it's the latter then OP isn't the person to be finding out, but she should report it as a safeguarding concern so it can be investigated by the right team.

she said the mother is not germophobe doesn't go anywhere

That is again a judgement from OP. It could be factual or it could be OPs interpretation, so if the OP genuinely believes there are grounds to be concerned about safeguarding she should report it relevantly so the family can receive support.