application- daughter want to go to different school to her brother,

[Mummybear01]

my son attends our nearest school (he’s very happy there) but my daughter would like to attend a different school.

she has dyslexia and her would get more support from the her preferred school as the resources for SEN support are stretched at my sons school due to the difference in demographics.

I have placed my sons school as our 2nd option- do I declare the sibling link, would this lessen the chance of us getting our 1st choice.
TIA

Won't make any difference to first preference. Might help with getting second if first is full.

If your daughter qualifies for a place at your first preference (usual criteria for most people is distance after things like LAC) then she will get a place there.

If she doesn't qualify because you live too far away, she will get a place (assuming one is available - sounds likely) at the school your son is at, if you list it as second preference. If you mention the sibling link that will strengthen your chance of a place there (assuming it is a criterion) but no, it will not affect your chance of gaining a place at the first preference.

No they will only look at second preference if she doesn't get her first choice. They are not allowed to take lower preferences into account when deciding whether she gets her first choice.

You can check the criteria in detail on your LEA website. They should be clearly stated and will be more reliable than anything we can tell you.

If the sibling link is something which is taken into consideration when the school's oversubscription criteria are applied in order to rank applicants, then there should be a formal way of indicating this when you name the school as a preference, and yes, you should indicate a link, so that your DD is ranked under the correct criterion.

If it is an oversubscription criterion, but there is no 'built in' way of stating this (e.g. a drop-down checklist of relevant criteria), or it isn't a criterion, in the former case, you should put this in the freehand 'Reasons for wanting a place' and in the latter, you still can if you want to. The difference being that when yhe school is informed of the reasons, if it's a formal criterion, it has to be acted upon, if not, it can't be (but to comply with admissions legislation, you jave to be given the opportunity to state whatever your personal reasons are for wanting a school anyway).