Have gone through a solution but I'm way off.
Market Sizing/Estimation: How many K-12 public schools are in the US? How would you estimate this?


It seems to be a standard market sizing that you can tackle starting from total american population, as suggested by others.
If you want to impress you interviewer, once that you have done your estimation, propose to do a sanity check of the result following a bottom up approach. One way could be to list the K-12 schools of your town, calculate the ratio schools/population and apply this ratio to the national population.
Hope it helps,
Luca

Hi,
Using the standard approach of US population at 320M, avg life expectancy of 80 and equal population distribution you get 4M*12 or approximately 50M children of school age in the US which is more or less what the internet says as well.
Where this gets confusing is total school size - elementary school sizes are much smaller as the costs to run them are lower and there is decent teacher availability (~250 per school), secondary schools are much bigger in size given the higher costs and bunch of other factors such as teachers, school zoning etc (~1,000 per school). If you take a rough average of 500 students per school you end up at ~100,000 schools which is close enough to 132,000 as per the census
Hope this helps,
Udayan

Hello!
In order to help you better: is this part of a case -where you are given a bit more guidance- or is this a brain teaser?
Cheers!

Hi,
I would estimate:
- N. of boys, starting from US population and assuming a constant population for each age group
- % of boys enrolled in K-12 schools
- % of public K-12 schools
- average boys per class and average classes in a school
Hope it helps,
Antonello










