Elementary School
The guide lists the Elementary School as a Little Hamlet unlock at 500 population. It describes it as the first building that provides education to child citizens and recommends constructing it early because educating citizens takes time.
How it works
Education lets residential areas level up; leveled buildings can house more families and pay additional taxes. The guide also says educated citizens benefit industry. The excerpt does not provide a capacity, coverage figure, or upkeep cost for the school.
When it helps
Consider it early if you want education to begin developing over time.
Read the supporting references
Original Cities: Skylines milestone progression and selected unlocks. Excludes Cities: Skylines II systems and modded unlocks. Guidance explains the referenced mechanics; it is not a tested damage ranking. Check the stated edition and source version before applying a patch-specific detail.