What a first lesson is for
A first piano lesson is not the start of the curriculum. It is the meeting before the curriculum begins, and most of the work in it is listening rather than teaching.
A teacher who has been in the chair for a while uses the first lesson to learn three things: what the student has already met, what the student can hear, and what the student finds easy to enjoy. None of those questions are asked directly. They surface through small tasks, short conversations, and a few minutes at the keyboard.
Almost no first lesson covers reading, technique, and a piece. There is not time, and trying to cover all three usually leaves the student remembering none of them. A good first lesson does one thing well and leaves a clear thread to pick up the following week.