Confusing GPA calculations - help!

<p>I manually calculated my GPA from 9th grade (I'm in 10th grade now), and it's different than the GPA my school calculated. Can you help me see what I'm doing wrong, and how to calculate my GPA if I get straight As for the rest of high school? (H - honors, R - regular, AP, IB, S1 - Semester 1, S2 - Semester 2)</p>

<p>9th </p>

<p>S1:
H - B, B, A, A, A, A
R - A</p>

<p>S2:
H - B, A, A, A, A, A
R - B</p>

<p>My Calculation - 3.7143
School Calculation - 3.8182</p>

<p>10th, 11th, 12th</p>

<p>S1
H - A, A, A, A, A, A, A
AP - A, A, A, A, A, A, A, A, A,
IB - A, A, A, A, A, A</p>

<p>S2
H - A, A, A, A, A, A, A
AP - A, A, A, A, A, A, A, A, A
IB - A, A, A, A, A, A</p>

<p>(7 classes per year)</p>

<p>How many Bs can I allow to get at LEAST a 3.8 GPA?</p>