Actually really true, since people only can remember people if they have it in their long-term memory, unless they are the same grade as you.
The longest time you can remember elementary students is 5-10 years (long-term) or at lowest, 5 days. (Short-term).
But since people say Short-term memory lasts shorter than usual (even though I experimented my short-term memories for more than a few days to weeks) I believe this may not be true.