State education officials say students in charter high schools aren't performing as well as their counterparts in regular high schools.
But the state also says students in charter elementary schools do better than their peers in regular schools.
Middle school scores were about the same on the Colorado Student Assessment Program tests.
Jim Griffin of the Colorado League of Charter Schools says there are 42 charter high schools statewide, and 25 of them serve high-risk populations. He says that might be why test scores are lower in charter high schools.
The figures come from a new report from the state Department of Education.
The report says charter-school students generally made bigger gains in reading, writing, math and science over the past three years than students in traditional schools.