I can’t speak to Montessori specifically but I have a freshly turned 5 year old with adhd combined type. He was in a Reggio preschool for 3s and 4s and is doing prek at at a more structured school. The structure is much better for him. Reggio is fine for a NT kid, and I think very small preschoolers should be just playing anyway, but at kindergarten age personally I would move on from the Reggio and Montessori based philosophies, especially for a very self directed child. Self directed usually means they are struggling in their environment for whatever reason, be it adhd, sensory processing, learning disabilities or spectrum based disorders. I can easily see a Montessori type environment masking those issues.