My DS6 was in Spanish immersion Kindergarten this year and, for him, it was a mistake. We thought it would be more challenging for him. After having him privately tested this winter with a high GAI on the WISC IV we started having meetings with his school. They would not give him more challenging math so we started EPGY at home. He asks to do "Eppy", as he calls it, as soon as he gets home. It is amazing how rapidly a mathy kid blows through it!
We have decided to pull him out of immersion this fall and are transferring to him another school in the district that has a separate gifted classroom starting in 2nd grade. His current Principal actually admitted to me in one of our meetings (amazing how many meetings you get with high test scores) that none of the 1st grade Spanish teachers would be able to accelerate or differentiate curriculum for him. So frustrating!
Initially we really wanted to keep him in immersion. The school lobbied hard to keep him. After much deliberation we are very happy with our decision. My DH and I feel that he can already understand, read and write Spanish after a year of 1/2 day K I'm sure he can pick it up later if he is interested. Right now it's more important to get him excited about actually learning at school, hopefully!
Regarding DYS his FSIQ meets the minimum. Our son's memory and speed scores were much lower than his others so the Psychologist used GAI like many of the kids geofizz referenced. For DYS we used the WISC IV and the Woodcock Johnson Achievement test to qualify. He was just accepted so we are learning as we go but I highly recommend it!
Feel free to pm me if you want to talk immersion. Good luck!