But few, I think realize that they also met in synagogues. For the first fourteen years of the church, the church was exclusively Jewish. And these Jews had been meeting in the synagogue all their lives. Once converted, they did not cease this habit; in fact, Yahshua expected them to continue that habit, Saul expected that's where he'd find these "heretics", and James refers to their synagogue meeting.
HCSB John 16:2 They will ban you from the synagogues. In fact, a time is coming when anyone who kills you will think he is offering service to God.
HCSB Acts 9:1 Meanwhile Saul, still breathing threats and murder against the disciples of the Lord, went to the high priest 2 and requested letters from him to the synagogues in Damascus, so that if he found any who belonged to the Way, either men or women, he might bring them as prisoners to Jerusalem.
HCSB Acts 26:11 In all the synagogues I often tried to make them blaspheme by punishing them. Being greatly enraged at them, I even pursued them to foreign cities.
YLT James 2:1My brethren, hold not, in respect of persons, the faith of the glory of our Lord Jesus Christ, 2for if there may come into your synagogue a man with gold ring, in gay raiment, and there may come in also a poor man in vile raiment,3and ye may look upon him bearing the gay raiment, and may say to him, `Thou -- sit thou here well,' and to the poor man may say, `Thou -- stand thou there, or, Sit thou here under my footstool,' -- 4ye did not judge fully in yourselves, and did become ill-reasoning judges.