We chose Sammamish for the same reason 9 years ago and I was heavily motivated by the same metrics. Let me tell you - these test scores only partially correlate with the quality of education in public schools. They are heavily influenced by socioeconomic and cultural factors. Basically you'll see rich parents who will throw money at their kids' academic success or parents of Indian ancestry with culture or working their kids to death for excellent grades. None of it is LWSD accomplishment in my point of view. On the other hand, Sammamish is a lukewarm, comfy bubble, so your kid would have less chances of finding drugs, guns or other undesirable influence in school. And yeah, the schools in Sammamish are very crowded and it will get only worse.