Continue using the low shelves you used when your child was younger, but as they grow, exchange the toddler toys for puzzles, books and other age-appropriate activities.
It's important to note that implementing the Montessori method for your child at any age does take some advanced planning, but perhaps even more so with school-aged children. Practical activities such as cooking, cleaning and reading are essential to incorporate into your home. Continue using the low shelves you used when your child was younger, but as they grow, exchange the toddler toys for puzzles, books and other age-appropriate activities. You can incorporate items that reinforce what they've been learning in school — however, the point of your efforts is not to overwhelm them with book knowledge, but to find practical ways to teach them everyday skills.