Economics is a great course helping children to understand the world.
Some schools provide lessons in economics during elementary school. However, economics as a comprehensive curriculum is most often taught in high school. Waiting until high school to study economics is fine.
Especially if a child needs economics for their major or as a general education requirement, they should consider taking economics at a local community college or as an independent university course.
There are also several other excellent options for studying economics, including the below.