Most schools came out of the last few years running both, without ever deciding to. Some classes are in person, some online, a few are nominally hybrid, and nobody has asked whether the mix makes sense.
Running both is not free. It is two schedules, two sets of expectations, two ways for a lesson to go wrong.
What genuinely works online
Adults with a specific goal. Business English, exam preparation, one-to-one. They are motivated, they can operate the software, and the convenience is worth more to them than the room.
Anything where your catchment is the constraint. If you are the only school teaching a level within an hour's drive, online is how you serve that demand at all.
Make-up and catch-up sessions. Low stakes, small numbers, and it solves a real scheduling problem - see the make-up class policy.
What usually does not
Young children. Not because it cannot be done, but because it is exhausting to teach well and the parent is effectively conscripted as a teaching assistant. Retention tells the story quickly.
Large groups of mixed level. The teaching techniques that hold a room together do not survive a grid of faces.
Anything a parent chose partly for the childcare. An online class at 4pm does not solve the problem they were actually buying a solution to. This one is rarely said out loud and matters more than anything on this list.
Decide with your own numbers, not the argument
You already have the data: attendance and retention by class. Split it by delivery mode and look. Online classes that hold 90% attendance are working. Ones at 70% are being tolerated until the term ends.
Do that before reading anyone's opinion, including this one, because it varies enormously by market and age group.
If you run both, keep them genuinely separate
The failure mode is the half-hybrid class - some students in the room, some on a screen, the teacher serving neither well. It is almost always worse than either done properly.
Separate classes, separate slots, and priced according to what each actually costs you to deliver.
A class that is both is usually a class that is neither.
And make joining trivial
Whatever you run online, the parent should not need to find a link. It belongs on the same screen where they see attendance and fees. If joining takes three steps, week three attendance will tell you about it.