By the cunning device of having more than one classroom
Each stage of the course lasts roughly three months (give or take a few weeks here and there). After one course has completed one stage, the next lot start and do that stage, hence courses start at three month intervals.
You'll start with the Basic course. Once 207 (which I think is the March course) finish the Basic Course in June they go on to the rating courses and 208 will start the Basic course. And so on.
As a minimum Area folk spend 9 months at college, single-rated airports folk 6 months, regional airport folks 9 months, longer if recoursed due to failure or on medical grounds.