Please help me identify this short story of speculative fiction about time travel (or maybe more accurately, time shifting) which I read some time in the late 1980s or early 1990s. I may have some of the details wrong but I'll try to summarize what I remember as well as I can.
The story was set in the present day and concerned a boy who somehow found himself living several minutes in the future. He arrived at school took his seat at his desk, but despite greeting them none of his classmates seemed to take any notice of him. When he raised his hand to answer a teacher's question, the teacher ignored him, even after he started frantically trying to get her attention. However, several minutes later his classmates said hello and the teacher acknowledged his raised hand, and then she became annoyed that he was continuing to wave it around and act as though he was trying to get her attention. The boy then realized what was happening: whatever actions he took did not have any effect on the rest of the world for several minutes; there was some sort of fixed time delay after which his motions and speech became visible. He became frightened, and left the school. He came to a road and speculated on the dangers of crossing it—that is, what would happen if he safely crossed it now when it seemed to be clear, but then a few minutes later a car appeared and struck his after-image?
That's all I can remember but hopefully it's enough for someone to go on.