Is there any way to call for a school to change its admissions policy?

Gosh yes I'd forgotten about the different half terms. This year they aligned, two years ago they didn't. This year my two have different Easter holidays.

I guess that the problem is that it is a bit like the scenario where one child has a private education and the other one doesn't, it can lead to resentment within the family. The children are just 10/11, they don't have an adult's perspective.

80% does seem very high though. Is it a fairly new system - so could they still have a lot of children who got in a few years ago and be working through a bulge year type explosion in siblings? I would have thought that around 50% would be more normal in which case only taking 20% oldest/only children might work in your favour in a few years as then there might be fewer siblings. Having some sort of 'siblings must live closer than x miles or in catchment' only really works if there is a catchment. I would feel most sorry though for the children living next to a school like that whose numbers don't come up, and are probably further from other schools so don't get in on distance.

There are still benefits at secondary age to having siblings at the same school. Same holidays and INSET days, hand down uniform if the same sex, same uniform supplier, same transport, same rules and policies, same method of communication, no clashes of parents meetings, sports days etc, more continuity with knowing teachers, systems etc. Every family with a child already at the school will have faced the same issue with their first child so it's not really unfair in that sense. I live in a town with two secondaries which are both very good and not oversubscribed, every single family I know (SNs apart) has sent all siblings to the same school.

Oh and sibling priority just makes sense. Many parents struggle to organise things around school as it is, attempting to do it around 2 schools would be a right pain.

I actually think they've got it spot on. Giving everyone who doesn't meet the first two criteria an equal chance would surely provide a better mix of pupils rather than what happens in a lot of places where only those who can afford to live in catchment.

I'm not in the UK. Quality school places are in massive demand. If you are offered a place, you grab it.
So, next door have 2 kids. One is at each of the 2 British schools here. Half term didn't align. Easter - one common week, with the second weeks being seperate. Summer - one kid finishes for the summer 4 weeks before their sibling. I assume there will be similar discrepancies for the start of next year.

So, I'd say aligned holidays would be of interest.

Also, a tiny proportion of parents volunteer for things. If secondary makes similar requests for assistance, and you have 2 kids at different schools, will you volunteer to help?

Whilst I think it is unfortunate, I think sibling link for in catchment or kids not given a choice should remain for secondary.

My brother is in the situation that his DS may not get into the same school as his elder sister (she got priority because of her SEN). If he doesn't get in it will be a nightmare complicated by the eldests Sen.

Ive got two children at two different schools. It is very challenging & only works as dh teaches in one of the schools. There are frequent clashes of events.

I don't know about other areas but there are only two single sex schools near to me & they are in the same town, one boys & one girls. They co-ordinate dates in ways that other schools would not.

Are you sure about the 80 percent, that's exceptionally and unusually high.

This is normal policy for many schools and I think it makes sense for families. I also doubt you will change it. Because the parents with more than one kid will campaign against you at a min, and apparently there is a lot of them...😁

80% siblings? Blimey- that's a lot! Was it an exceptional year?

You'd be better trying to lobby for the change with as many other prospective parents as possible rather than be a lone voice. Certainly schools do change their criteria, several in my area have moved to admit siblings only in catchment as priority. Siblings outside catchment have less priority than children with no sibling in catchment.

Plenty of siblings go to different schools at secondary level, especially if the only options are single sex schools.

They might never change it but only you can decide if you feel it's wasting your time to try. Personally I'd give it a go plus putting some thought into realistic other options.

So are you saying 80% of the children are children in the care system?

I tried this in one if our local girls schools.

I emailed the school governors with my points and they discussed it at a governors meeting. In the end they decided to stick with it but at least I tried. I don't even want DD to go there, I just wanted a choice. The school decided that it was better for the school to have interested families knowing all their girls can go there. Basically you get your first child in then move but all the sisters go, but this shows dedication and motivation...

So, get a letter together and send to the governors

The admissions criteria must be published for consultation every year. This would also be a good time to contact the school and out your points across. Look on their website for the consultation.

Could you organise other parents, might be better than being a line voice?

Do you only have one child?
Having two or more kids at different school means you have to plan two parents evening on two dates, two sports days, two this, two that and two the other. Learning about the policies and procedures of different schools can be a right pain. Just because the children may travel on their own, it isn't the only thing to consider.
They'll never change it, but the way. You are wasting your time.
Also, isn't distance a criteria?