@GemmaV
Isn't it Andover's average score which is 93%? That's what it says on boardingschoolreview.com. And directly from the Phillips Andover website:
What is the average GPA/SSAT score of applicants that are offered admission to Andover?
Although the Andover admissions committee has no minimum grade or score requirements for acceptance, the average Andover student maintained an "A" average at his or her previous school and scored in the 93rd percentile on the SSATs.
Phillips Academy - FAQs
And even though 93% is no way the cutoff SSAT score for Andover (I don't think it's that high) I think it'd be safe to aim for close or higher than that, because there are going to be a LOT of applicants who are in the 99 percentile. But even if she gets in the 80th percentile, I doubt she'll be rejected for that. Good luck to your daughter, Sadie!