Should one declare marital status to schools where there is competitive assessment?

[Homely1]

Does this pay a role in as much as the school may feel the child will not keep up? In theory, it should not be a consideration but if they have a 'like' group of children, would they use this to filter?

No, ability to parent isn't based on how many people are in the household.

How many families, who are 2 parent households, have one who works long hours and so isn't present with children often?

One parent can do as good or better a job as 2,3 or 4!

Pretty sure that is completely irrelevant.

Schools couldn't care less, they want the children who get the highest mark in the assessment. End of. Plenty of children of single parents/cohabiting parents at my dcs' very competitive school