Acts 15:13
And after they had become silent, James answered, saying, "Men and brethren, listen to me: Simon has declared how God at the first visited the Gentiles to take out of them a people for His name. And with this the words of the prophets agree, just as it is written: 'After this I will return And will rebuild the tabernacle of David, which has fallen down; I will rebuild its ruins, And I will set it up; So that the rest of mankind may seek the LORD. Even all the Gentiles who are called by My name, Says the LORD who does all these things.' On the contrary, I think the sixth grader would see that James repeats Simon's point and then proves it with part of Scripture. He is saying the the words of the prophet agree with Simon. He is not talking about something that comes after Peter's point. Step back and read the verse without your preconceived theological notions.
The prophet he is referencing is Amos as in 9:11-12 who says that there will come a day when God will raise up the tabernacle of David .... . . . . so that they may possess the remnant of Edom [the Palestinians?] and "all the nations which are called by my name".
They can't possess all the nations called by God's name until the Gospel goes to them and they were discussing in the council of Jerusalem whether it should or not? Peter said it should and already is beginning to. Amos said it will. They agreed, because before the tabernacle would be rebuit the Gentiles had to be brought into the kingdom.
The point was first things first --