Generally, it's best to take the ERB (ISEE) in December. The ISEE is an academic-based test, the more you have learned, the better you do. You're graded against a same-grade based peer group. From the ERB, the people who administer the ISEE: It is important to note that the ISEE may not be taken for … Continue reading ERB (ISEE): When Should I Take the ERB (ISEE) to Get Into a NYC Private High School or Middle School?