Cheryl Broad has had three children at King's school in Peterborough where she is head of history.
If King's, in Cambridgeshire, had not given places to her children she would have faced problems with timetables and school holidays as the family live in a different county.
She said: "The schools in Rutland have different holidays. When the children were young, I would have needed to find people to look after them.
For things like general organisation, running the household, it is more convenient having them at the same school. But I also know they are getting quality education."
One child, James, left King's last year and the other two Matthew, 16 and Ellen, 14 are still at the school.
Mrs Broad, who has worked at the school for 10 years, said: "I don't think it's unfair, it's perfectly reasonable. If it helps to retain staff, I think it's fair."