Knowledge of music theory becomes more and more helpful as students progress in learning their craft. Understanding the inner workings of how a piece is put together can cut down on practice time (and frustration) thereby helping to master a piece more quickly and confidently. Theory is not just about being able to read notes and rhythms, but about understanding the structure and musical flow (phrasing) of a piece.
Our teachers generally make theory a part of beginner lessons. As students progress through higher levels of study, separate theory classes are recommended. Royal Conservatory of Music (RCM) requirements start at level 5 and students wishing to pursue music in university definitely need theory prerequisites under their belt!
Talk to your teacher early on in the year if you would like to take separate theory classes to complement your regular lessons.