Iowa Code § 275.20: Separate vote in existing districts.

The voters shall vote separately in each existing school district affected and voters residing in the entire existing district are eligible to vote upon the proposition to create a new school corporation and on any additional provision authorized pursuant to section 275.12, subsection 6. If a proposition receives a majority of the votes cast in each of at least seventy-five percent of the districts, and also a majority of the total number of votes cast in all of the districts, the proposition is carried.