We had the same problem a year earlier... but were caught flat footed. Our own fault.
Right before Kindergarten, after 3 years in montessori preschool our kiddo was SOOOOOO excited about "big school" that we just sent him. Huge mistake. Like yours he was doing +-x/, reading chapterbooks, using the real terms for things... Normal run of the mill Montessori things. We were in the 300's on the waitlist for a 20 spaces available K-6 montessori class, so we went to our local school (rated top, btw... but as Thea said... ratings are based on % of students being AT grade level... and at grade level varies quite a bit. In our district that means knowing your colors by the end of K, and being able to add and subtract by 3rd grade). That is officially the LAST time before he's 14 that kiddo gets to choose what school he goes to. Not that he made the choice, much less knew that the choice was his... but he wanted, so we did. Oy. Lesson learned.
By christmas break the little boy I knew and loved was disappearing. He used to be a bright, curious, funny little guy who loved his friends & learning/school above all else. By break he was skipping off the bus waving at his friends until the bus was out of sight and then he'd cry for hours. He still loved his friends, but he was shutting down inside. He was miserable, and bored out of his mind... but didn't want to make his friends feel bad so he'd "pretend" which made him very very tired. He had a phenom teacher with over 30 years exp, who was completely aware of the problem and did her very best... but she was literally begging us to get him transferred before he turned his mind off and just decided to hate learning.
In our area (seattle) there is an incredible gifted school... where the kids are grouped together by age, but work at their own level. They just get used to Susie being a "science girl", and Billy being a "numbers guy", and Jonnie being a "languages" guy. AKA... they get to be with their developmental peers (which, by and large, is all about sense of humor/what's "funny") and work academically at their own pace. The kids were also encouraged to be kids (as in running, skipping, or pretending to be a giant bug or rocketship) to or between classes was encouraged. Not a stay in line/stay within the lines kind of place. Killer school. It would have meant a 40 minute drive each way, but it would have been worth it.
And so far out of our budget as to be impossible. So we homeschool. Which was scary, but has turned into a giant adventure... with a social calendar so full that I have to seriously put breaks on it.
Anyhow... just our experiences
- kids choosing their own school before they're cognizant of all the factors involved is just plain silly (btdt)
- look for a way to either continue with the montessori education, or a gifted school... most of which teach at least 1/2 way montessori
- look for a gifted school over a "highly rated" school