Question: I have been to four different high schools in four years. How will this affect my application in the eyes of admissions committees?
In the admissions world, there are both pros and cons to your situation. In the plus column, this will give you the chance to show admission committees that you are flexible and able to adjust to changing circumstances (assuming, of course, that you are). If your moves involved relocating to different countries--or to very different places within the same country--then this could work in your favor, too, because, again, it will allow you to show off uncommon adaptability and varied experiences. (This could be brought out in an essay, in a supplementary unsolicited essay or letter, or in your school counselor and/or teacher references.)