As long as you have taken all of the courses necessary, I dont see any problem with taking it in August. If you havent finished physics or organic, definately DO NOT take it! I think taking it in august will give you several advantages. First of all, if you do well, you wont be stressed out about it all throughout your junior year. From experience, that is a BIG plus. Also, if you need to retake it, you can do it next April, and you won't be behind in submitting your application. However, if you don't feel completely ready or prepared to take it in August, I would recommend waiting till april.