The Lifespan Development Psychology DSST is Prometric’s counterpart to the College Board’s Human Growth and Development CLEP. The good news is that studying is relatively straightforward if you’ve already taken the Human Growth and Development CLEP and your school grants credit for this exam as well. The bad news is that many schools consider this duplicate credit, so be sure to check with your academic advisor before registering. If your school does accept the credit, there’s even more good news—this exam hasn’t been updated in a while. As a result, there’s a wealth of information available about what you’ll need to study. Also as noted above, the Introductory Psychology and Intro to Educational Psychology CLEP are exams with a decent amount of overlap with the Lifespan Development Psychology DSST. If you could score some credits by taking those, I'd probably aim for those first and then take this one.