In a large hall, the teacher teaches the average student. In a small batch, the teacher teaches each student — and that difference shows up in test scores within a term.
Small batches make three things possible: every student is asked a question in every class, every answer sheet is checked by the teacher who taught the chapter, and no doubt waits more than a day.
It also makes weaknesses visible early. When a student's accuracy drops in Organic Chemistry, the faculty notices in week one, not after the pre-board.
Our batch strength is capped by design, which is why seats for each new session are limited.