A study done by the Center for Education Reform, Annual Survey of America's Charter Schools: 2005 Data, reports:
On average, charter schools enroll 297 students, about half of the number attending conventional public schools. According to the National Center for Education Statistics, in 2003-04, the average number of students per school was 438 in primary schools, 616 in middle schools, and 758 in high schools. Research indicates that smaller schools typically are more advantageous for learning, depending on the programs being used and what is expected.
The number of charter schools operating in 40 states and the District of Columbia in the fall of the 2005-06 school year stood at 3,617 with more than a million students enrolled.