Sounds like maybe a mismatch with the preschool? My DD did better in a non-academic play-based preschool.
IMHO an updated IQ score is unlikely to tell you anything that her previous one didn't. If you're wanting the preschool to either give her harder work, or excuse her from academic skills she's already mastered, achievement testing might have some value - but unless there are absolutely no other preschool choices available to you, I'd anticipate it would be easier to find a preschool that's a better fit.
