Answer
Actually it was Jordan who drew my attention to the "holy convocations." I think that from the time of Moses there was some kind of Sabbath meeting. I presume that such meetings were held locally in various places after Israel entered the land, and in time they were called by the name "synagogue," though we don't see that name used in the Bible until the NT.
Jim and I may not agree entirely on the nature of post-resurrection Christian worship. I think (with Gerhard Delling, for example) that the original post-Resurrection Christian worship (1 Cor. 14) was not very much like the synagogue. The original Christians were Jews, and they went to synagogue on the Saturday Sabbath. Then on the First Day morning, they gathered to celebrate the Resurrection. They had already had their synagogue worship; now they gathered to do something different. From Paul's description, it was a bit of a free-for-all, and it needed some structure and order.
In time, the Christians were expelled from the synagogues and/or left voluntarily. At that point, they evidently felt a need for something like a synagogue service under Christian auspices. So the First Day worship became more like a synagogue. But I don't think that structure is essential to Christian worship.
I'm not sure where James' language applies in this development. It may be that the Christian house churches were called synagogues from the beginning; but that may or may not have implications for their style of worship.
As Jim points out, there is a lot of temple symbolism in passages that refer to Christian worship, and I think it's right to say that temple and synagogue are both fulfilled in Christ, and in Christian worship. Unlike Jim, I don't think that fact dictates a certain liturgical order. I think the pendulum has gone to the opposite extreme from 1 Cor. 14 in many places, and it's time to go back to more of a free-for-all.
Answer by Dr. John M. Frame
Dr. John M. Frame is Professor of Systematic Theology and Philosophy at Reformed Theological Seminary in Orlando, FL.