First of all, many colleges have specific admissions requirements, especially in the areas of science and math. If you wait until your senior year is underway to check into the admissions requirements of colleges that interest you, you may discover too late that you cannot get into those institutions because you have not taken the required courses. Also, some colleges have certain ACT or SAT score requirements. If your scores are not high enough to meet their standards, you may need to try again. The national test dates will determine when you may take these tests, therefore limiting your chances of raising your score before the application deadline. If you decide during your junior year where you may want to go, you will have more chances to take the test and to meet the college's score requirements.

Some of the more selective colleges want you to apply as early as your junior year. Others prefer that you apply during the first month or two of your senior year. Some have later application deadlines, but their scholarship deadlines may be as early as December 1. In such a case, the college may accept you if you wait until February or March to apply, but you will not qualify for any of the campus-based scholarships. College tuition is expensive, so don't let your procrastination disqualify you from any financial aid that you might have received if you had applied earlier.

http://www.sci.wsu.edu/math/placement/

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