For purposes a claiming a dependent (but not for education credits), high school does count. The IRS defines "school" this way:
School defined: A school can be an elementary school, junior or senior high school, college, university, or technical, trade, or mechanical school. However, an on-the-job training course, correspondence school, or school offering courses only through the Internet doesn't count as a school.
Vocational high school students: Students who work on “co-op” jobs in private industry as a part of a school's regular course of classroom and practical training are considered full-time students.
Page 12, https://www.irs.gov/pub/irs-pdf/p501.pdf
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
