This old thread put the cutoff at 220-230 Spring MAP-M
https://www.dcurbanmom.com/jforum/posts/list/733106.page
But there is a wide range because each school has to have a whole number of Compacted classes, so it has to set the cut off either higher or lower to land on a whole number of classes, depending on the mix of kids. For kids near the borderline, there's not a huge difference between compacted math with no enrichment, and regular math within enrichment. There's a lot of overlap between one great level and the next, or one math level and the next.
You still have a chance to move up or down at start of 5th and 6th grade based on their growth. (And maybe even 7th or 8th if they do well enough in their pre-pre-algebra class that they can jump up to pre-algebra or algebra).