I have a kindergartner at STEM and I'm happy we took the plunge "into the unknown". I'm constantly singing the praises of our K teacher and the rest of the dedicated staff, this school is doing cool stuff. I should say they're doing cool stuff with what they have - the school district has been slow to follow through with some of its promises (like wsmama3 said, for instance, we just got a playground, and wifi is still on the way...). My kid is more of an artistic type, and I wondered how he'd responded to STEM project based learning. It turns out he's super excited about science (his favorite subject) and reading. in other words the STEM curriculum is reaching more than the just Lego maniac kids. Diversity is important to our family and STEM seems more diverse than our reference school - a big plus for us. The uniforms are easy and feel purposeful - I'm really glad the Design Team established that policy. My favorite aspect is the community. I didn't expect to make such good friends but the feeling of welcome and belonging is strong. We've taken this plunge together and are building a strong school.
Others have listed the PTA site, you may also want to search on WSB for discussions about K5 STEM. Many people have written their sentiments on the forums and main page comments.