An adult is about to sit down and use your prototype.
Your job for the next 15 minutes is to watch and listen. Not explain. Not help. Not apologize for anything that doesn't work.
What they struggle with is your most valuable data of the entire day. The same adult will return at 2:15 PM to see what changed. That before-and-after arc is the core of your pitch.
The adult has finished using the prototype. Now you talk to them. One student asks the questions. One student captures the answers. The other two listen and can each ask one follow-up: "Can you say more about that?"
You have 2 minutes before you move to the Synthesize page. Use them.