Should I take a higher dose?

Okay, this is a followup question to one I had earlier today. I took 30 mg of Vyvanse at 9:45 today. I did not feel any effect until around 12:00. Then I felt the effects until around 1:10 ish, and then it was gone, Is this normal or should I be taking a higher does, because one hour is not going to help me get me through a 6-7 hour school day.