Deborah Costello

Math Teacher

Deb Costello earned a BA in Mathematics from St. Olaf College and a Masters in Liberal Studies from Lake Forest College.  She spent 7 years at Lake Forest Academy in Illinois and 23 more at Trinity Prep School in Orlando, Florida before joining the Deerfield community in 2017.  She has taught all levels of math as well as well as psychology and a course in leadership and has served as a consultant for the College Board. 

Deb was an All-American swimmer in high school, a triathlete as an adult, and coached swimming at Lake Forest and Trinity.  She has also coached volleyball, softball, and bowling at various points in her career.  She coaches JV swimming at Deerfield.

Deb is an associate in Mather and lives a few minutes off campus.  She is married and has two sons, one a senior at Holy Cross, the other a sophomore at Emerson.  She enjoys photography and her black lab, Lucy.