Video from wheatoncollege
"Dr. Jordan Ryan is Assistant Professor of New Testament at Wheaton College and author of The Role of the Synagogue in the Aims of Jesus, among other things. The Greek word for “church/assembly” (ἐκκλησία, ekklesia) occurs in the Gospels only in Matt. 16:18 and 18:17. Dr. Ryan observes that there were a couple of types of synagogues in the Jewish world, and Matthew might be using the word ἐκκλησία in Matt. 18:17 to demarcate an “association synagogue,” i.e., a Jewish synagogue that was less public and more private, in this case comprised of Jesus followers." from video introduction.