however often resisted by US school administrators. Early entrance to middle school or high school: Early entrance to high school enables the student to avoid being stuck in the "holding pattern" of middle school. Grade skipping One of the best-known forms of academic acceleration, grade skipping involves moving the student ahead one or more grades. Where grade skipping is inappropriate, other forms of acceleration may be recommended instead. One metric used for determining whether grade skipping is appropriate is the research-based Iowa Acceleration Scale, which entered its third edition in 2009. In particular, the IAS identifies four conditions under which grade skipping is unwise: If the student's intelligence quotient is less than 120 (i.e. less than one standard deviation above the mean) If the student has a sibling in the student's current grade If the student has a sibling in the grade into which the student would accelerate If the student does not want to skip a grade Extracurricular programs In extracurricular acceleration, students elect to enroll in weekend, after-school or summer programs that confer advanced instruction and/or credit. In some cases this will allow especially radical acceleration in content, such as a primary-school student taking university-level extension classes. Self-paced instruction In self-paced instruction, the student proceeds through learning and instructional activities at a self-selected pace. Self-paced instruction differs from continuous progress instruction in that the student has a greater degree of control. Credit by examination Often referred to as "testing out", credit by examination involves giving a student advanced standing credit (e.g., in high school or college) for successfully completing some form of mastery test or activity. Studies of gifted college students suggest that this may have slightly negative effects on psychological well-being. Multi-age classrooms Classrooms with students of diverse ages allow younger gifted students to be grouped with older students who are closer to their academic level. They also create opportunities for peer instruction, leading to heightened self-esteem in gifted students. Telescoping curriculum In a telescoped curriculum, the student is provided instruction that entails less time than is normal (e. g., completing a one-year course in one semester, or three years of middle school in two). Telescoping differs from curriculum compacting in that time saved from telescoping results in advanced grade placement. Subject-matter acceleration/partial acceleration This practice allows students to be placed with classes with older peers for a part of the day (or with materials from higher