The Odd & Even lesson is a Montessori favorite, and it doesn’t take a lot of material to make it happen. 1-10 numeral cards plus some counters, and you’re good to go.But…the extensions to this game can be really fun. They reinforce the concept of NUMBER SENSE and prepare your child for working with larger numbers. In our new Odd & Even set, featured here on our YouTube channel, we created Montessori cards that will take you from 11-20 as well, plus derivations on the classic lesson.