Parents buy a school, not a subject
The first question on every call
A parent preparing a child for entrance exams asks the same opening question everywhere: do you know these particular schools. The format differs between them, the timetable differs, and the family has usually already decided on a shortlist before they contact anyone. A centre organised by subject can only answer in generalities.
Cohorts by target school change what you can say
Grouping candidates by the schools they are sitting for lets you answer that question with something concrete, staff specialists against the cohorts that need them, and see which target schools you genuinely serve well rather than which ones you happen to mention on the website. It also makes the annual pattern legible: which schools drive your intake, and whether that mix is shifting.