I'm surprised you could get the STAR testing results now- normally they don't come in the mail until the end of august. Maybe the teacher glanced at his test quickly?
STAR tests are very, very simple. I would not rely on them to decide on a grade skip. For end of the second grade, they ask questions like: "Here is a clock. What time is it?" It's really an example of how the curriculum is dumbed down. You would probably get a better idea if you pay $500 for a Woodcock Johnson test, etc.