How does a city know, how many local grade schools are need?

Question

1. City Birth Records?
2. House to House Poll?
3. Status Symbol?
4. The local Parent Teacher Association?
5. Random counting of children?
6. The next time people vote, the question is included "How many children under 14 live in your physical home?".

Answer 1

Nothing that elaborate. It's mostly from the schools that are already standing and how crowded they are.

Answer 2

Districts also take a look at new housing developments, any changes in large employment within the area, etc. They also watch the pattern of enrollments across time.