Generate an 8-10 second video prompt centered on a classroom reaction talking avatar. Build it as a reusable video brief with three concrete beats: open by establishing an adult speaker or presenter, the classroom-style setting, and the dialogue context; move into the main spoken line or reaction beat with stable framing and clean lip-sync; end on a stable final frame that can work for a preview, lesson clip, or social cutdown. Anchor the sequence on natural facial motion, clear reaction timing, stable camera distance, and safe audience-appropriate delivery. Specify pacing, lens feel, camera distance, lighting, motion blur, and continuity rules so the output stays readable. Keep the speaker, props, location, dialogue text, and logos editable. Avoid real brand names, celebrity references, fixed IP, readable signage that cannot be changed, unsafe action, sudden teleport cuts, inconsistent scale, warped anatomy, and unrelated extra scenes.