From Business Insider: Some of the city's most elite private schools will soon require 4-year-olds to take a new, harder admissions test given on an iPad and designed to assess math and literacy skills. The educational services company ERB's Admission Assessment for Beginning Learners (AABL) will be given for the first time in October and is a significant departure from the previous, IQ-like test most New York City private schools required for the past…