Be careful when talking about schools in Spanish! If you’re talking about school in the general sense, use escuela. For grade school, elementary school, and grammar school, use escuela primaria. For high school, use escuela preparatoria, escuala secundaria, colegio, or instituto. Unfortunately, there is no term for junior high school. When you graduate high school, you attend la universidad. Do not use colegio because colegio refers to high school. College and colegio are false cognates. If you attended a junior college or a community college, you must use universidad because junior and community colleges do not exist in the Spanish speaking world. 

Students in the general sense are estudiantes. If you are a college or university student, you are either an estudiante, alumno, or alumno subgraduado. Graduate students are alumnos graduados or alumnos de posgrado.