I had it, woke up and knew I had to get it down on paper. I think it could be a really good story for someone to try to write.
A student in high school (either gender) doing a play in front of people. The student gets nervous to the point where they have to leave the classroom. Going downstairs, the student runs into three women who recognize the student as someone else. Not wanting to disappoint them, the student plays along. The student discusses what happened with them and asks for advice since the teacher hasn't followed yet. They suggest staying downstairs until the teacher finds the student, as opposed to the student's original plan of simply going home. The student thanks them and then gets up and leaves, walking around the school. In the office, he passes a beautiful young woman and her toddler on a changing mat (obviously she just finished changing the toddler's diaper). He looks at the toddler a moment, but continues on. As the student continues walking around, the student begins to wonder, "Are kids getting taller these days or am I shrinking?" The student eventually realizes that the latter is exactly what is happening. But not just shrinking to the point of getting shorter...the student is also getting younger. It turned out that the woman whom he passed earlier (the mother of the child that was getting changed) was a witch and, even though it was momentary, she noticed the student looking at her child and saw the look on the student's face. She knew what the student wanted so she wanted to give it to him. By the time the student realizes what's going on, it's too late. The mother finds him and takes him in.