It depends. I’m also applying to ten boarding schools, and have had the chance to meet with a ton of admission officials in person. It might just be the nature of the relationship we developed during the interview, but one admissions official basically told me that I could send in as many recommendations as I wanted, regardless of whom they were from. Yet, another admissions official from a separate school told me that I should only submit additional recommendations that are truly significant and show a different perspective from the rest of my recommendations.