I use a peaking factor of 6 for schools. I haven't seen any published information or data to back it up. An often used peaking factor is 4. In fact, I've met engineers who always use 4 no matter what the size or type of project it is. I figure a school will have a higher peak than an office or shopping mall. The oldest I've done is about 3 years old with no reported odor issues or other problems.
You could use the 10 States formula, which for a school of 1000 would yield 3.8. However, 10 States is based on residential populations which would have a lower peak than a school.
What peaking factor were you thinking of using?
What is the population of the school?
What are you allocating for per capita average daily use?