TOEFL 100 , better to have 110
But the most important thing, really, is not only the TOEFL. The school will also look at grades, extracurricular activities, SSAT scores, essays and recommendations. All those have to be good.
Minimum is TOEFL 100. But you really should consider other factors, not just TOEFL. Other factors include, grades, SSAT scores, extracurricular activities, recommendations, interview and essays.
