This examination of California's independent study high schools (alternative schools in which 75 percent or more of students in grades 9-12 are enrolled in full-time independent study) describes enrollment trends since 2001-02 and the number and characteristics of schools and students as well as teacher qualifications in 2006-07. The study used a merged school-level longitudinal dataset to track student enrollment from 2001-02 through 2006-07, and used school, teacher, and course-level datasets for 2006-07. The quantitative analysis contrasts the characteristics of independent study high schools with other non-traditional and traditional high schools. Qualitative data from the latest available School Accountability Report Card for each independent high school identified targeted student populations. Reported findings include: (1) In 2006-07, 58,788 students were enrolled in full-time independent study in grades 9-12 in California's 231 independent study high schools, an increase of 44.2 percent from 2001-02; (2) Approximately 54.9 percent of independent study high schools reported targeting a specific student group; (3) In 2006-07, the students population of independent study high schools was less diverse than that of other types of high schools, with larger percentages of White students and female students, and lower percentages of socioeconomically disadvantaged students, English language learner students, students with disabilities, and migrant students, than other types of high schools; (4) In 2006-07, independent study high schools were less likely than other types of high school to be located in urban areas, or to have been open before 2001-02; and (5) Teachers in independent study high schools were less likely than teachers in other types of high school to hold an advanced academic degree and a secondary subject-specific teaching credential. Two appendices are included: (1) Data Sources, Methodology, and Limitations; and (2) Descriptive Statistics. (Contains 4 notes, 1 box, 1 map, 5 figures, and 13 tables.) [This report was prepared for the National Center for Education Evaluation and Regional Assistance, Institute of Education Sciences (IES) by Regional Educational Laboratory West administered by WestEd. For summary report, see ED505662.]