Choose the angle for the action
Use a wide classroom to establish where everyone sits. For a conversation, choose a crop that leaves the faces clear and room above them for balloons. Check desk rows against the horizon and the character's eye level. A corridor is useful for arrivals and transitions between classroom scenes.
Keep the school recognizable
Record the board position, window wall, door and desk arrangement for your chosen classroom. Reuse the reference in later scenes and check these landmarks when you generate another shot. Select day or night according to the story, then inspect the actual image rather than assuming every edition shares the same architecture.