In the Montessori Casa, or classroom for three through six year old students, children ages four and older use golden beads, slotted boards, and wooden number cards to concretely learn quantities and numeric symbols for tens (numbers ten through ninety) in mathematical and conventional language following ample experience with quantities and numbers one through nineteen. My First Montessori Book of Tens, the sequel to My First Montessori Book Teen Numbers, is designed to help children strengthen their understanding of numbers ten through ninety-nine in preparation for more advanced mathematics exercises. Written and illustrated by AMI Primary Diploma holder Mary Da Prato, My First Montessori Book of Tens describes strategies used in the Casa to help children learn and understand tens as an essential prerequisite for counting to 1,000 and beyond. Also described are prerequisites and parallel activities which concretely introduce the quantities and symbols for units, tens, hundreds, and thousands.