What's the best online platform for teaching English to kids?

It depends on what you're optimizing for. Three broad categories:

General video tools (Zoom, Google Meet): Ubiquitous, parents and kids already know them, free for short calls. Designed for adult meetings, though — limited interactivity for young learners and no built-in lesson tooling. You'll bolt on slides, whiteboards, and games separately.

Marketplace platforms (Outschool, Preply, italki, Cambly): The platform brings you students and provides the tool, but takes a cut (often 20-40%) and owns the relationship with the parent. Good for getting started; bad for building an asset.

Purpose-built virtual classrooms for kids' tutoring (e.g., Koala Go): Designed specifically for young-learner ESL — interactive slides, on-screen activities, drawing and annotation, reward systems, and parent-facing tooling. You own the student relationship and the brand. Trade-off: you have to bring your own students.

A common path: start on a marketplace to get reps and reviews, then move retained students to a purpose-built classroom you control, where the renewal economics — repeat business, no platform cut — work in your favor.