They release in three big batches. One around 7am and a second around 6pm. There is a third, much smaller batch they release tomorrow morning. After that, they release as they clear potential problems. My kid got the 6pm batch last August and the 7am batch today.
There is apparently no correlation between where your kid lives and when the release happens. It’s just random.
The SAT subreddit is amazingly helpful. When the second batch release happens, you will be able to tell by checking it.
https://www.reddit.com/r/Sat/