- Meet our Staff -

highly trained professionals eager to serve you and your children.


Cassella Slater

Upper School Lead Guide

Contact Cassella

Cassella Slater is the Financial Officer, Children's House Lead Guide, and pedagogical director of the Upper School. While teaching agriculture in Ghana for a year, she unexpectedly fell in love with teaching and the adolescent age. She has a B.S. in Animal and Poultry Sciences from Virginia Tech, and completed her NAMTA/AMI Adolescent Training in Chihuahua, Mexico. She earned her AMI 6-12 Diploma from the Montessori Training Center of Minnesota. She has also earned her Masters of Education from St. Catherine's University.


Maria Valdivieso

Young Children's Community Lead Guide

Contact Maria

Maria Valdivieso, YCC Lead Guide, earned her AMI 0-3 Diploma at the Montessori Training Center of St. Louis. She is passionate about her work. In the YCC environment she speaks solely Spanish, allowing our children to be immersed in the Spanish language throughout their day. She has completed her AMI Primary Assistant training and is a loving Montessori mom of two!

Kaitlyn Lehan

Children's House Lead Guide

Contact Kaitlyn

Kaitlyn Lehan has a B.S. in Family and Consumer Sciences with a concentration in Child Development from Bridgewater College. She loves working with children and helping to foster their development each and everyday. She wants to make known that learning is a joyful and exciting experience we get to take part in everyday. 

Alejandra Guzman

Children's House Assistant

Contact Alejandra

Alejandra has been working with MMS since 2019. She has been an amazing addition to our staff and loves working with the children each and every day. Alejandra speaks solely Spanish throughout the day so the children have an immersive experience with two languages. The children love being around her positive and happy energy.  

Lupita Gutierrez


Contact Luptia

Lupita Gutierrez has energy that is unmatched. Lupita has earned her AMI 6-12 Assistant Certificate. She makes the each day engaging and exciting for the children. With a smile always on, the children love her! In the upper school and extended day environments she speaks solely Spanish, allowing our children to be immersed in the Spanish language throughout their day.

Lilly Bonnie 


Contact Lilly

Lilly Bonnie has been working as a teacher assistant with Middleburg Montessori since 2019. She is currently working on getting her teacher education degree. In her free time she loves spending time with her dog Bella, and enjoying her farm animals and her family.  She is at ease with any age child and brings joy to every interaction.


BethAnn Slater

Head of School

Contact BethAnn

BethAnn Slater, the Head of School, loves children and the development of children. She is the mother of 4 children, all of whom attended Montessori. She has an AMI Montessori 3-6 Diploma, a B.S. in Family and Child Development from Virginia Tech, as well as a Masters Degree in Early Childhood Education. She has taught for over 25 years both in public and private settings. Most recently, she earned her AMI 3-6 Trainer status. Currently, she trains adults in both Cape Town, South Africa and Dallas, Texas.

Phone:  (540) 687-5210

Mailing Address:

PO Box 35 

Middleburg, VA 

Physical Address

7274 Rectors Lane 

Marshall, VA 20115 

Middleburg Montessori School is a non-profit AMI Montessori School serving children birth through age 15.

©2017 by Middleburg Montessori School.

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