If it has to be one or the other, I'd go with Montessori, with the caveat that our HG+ son was bored stiff in a Montessori classroom.
If I had to do preschool over again, I'd look for a play based classroom that focuses on fostering imaginative play and social/emotional development.
How quickly was it apparent he was bored? Was the school willing pull appropriately leveled work for him? Was his school experience any better after leaving Montessori? How do you think elementary school would have looked for him if he’d been in a play-based preschool instead?
It took me a full year to realize that he had been doing the *same work* the entire time--work he called the "scratchy letters." When I realized this, I told him that if he wanted he could do something else, that he just had to tell his teacher that he was ready to move on. So then he moved on to some word thing that he did for *another* year. The thing is that he could already read simple text before he even set foot in the school (at age 2.5). He didn't need to go through the Montessori sequence. I told them all of this, but their stance was that the child needed to decide how to spend their day. I ended up homeschooling him after his time in the Montessori preschool. He did a two year stint at a private school from ages 10-12, and he is currently attending a few classes at the public high school.
I've now raised two kids to late teen/young adult ages. The reason I advocate for play-based preschool is that there is *plenty* of time for academics down the road. In fact, I'd argue that for gifted kids, there is *far too much time* devoted to academics, because they pick things up so quickly. A kid only has so much early childhood in which to play and imagine. I see now that those years are precious, and there is no reason to waste them on structured academic learning.
