It may be a “good idea” if the college is clearly your first choice, you have a strong curriculum your senior year, your grades from junior year were excellent, your standardized test scores are competitive, and you can complete your testing requirements by October of your senior year.
It may be “an idea” if you are on the “bubble” for admissions, you are a traditional candidate for that school, you may be a child of alumnus, you have a brother or sister at that school, you are an athlete (non-scholarship school), and your test scores and grades are in the middle 50% of accepted students.It may be a “bad idea” if financial aid is a major concern and want to compare packages, have weak junior year grades, your standardized testing is not complete or not competitive, you not sure if your really have a first choice college, you have not visited the campus, you may not be in the range academically of students who are typically admitted, and admission is an exceptional long shot.
Bottom line, check out statistics on the college’s website and speak to a college admissions representative directly about why you are considering early decision as an application method.