To get the IB Diploma, you need to complete 3 HL and 3 SL (or you can do 4HL and 2HL, I believe) courses meeting a “gen ed” type distribution – (1) English, (2) History/Social Science, (3) Foreign Language, (4) Math, (5) Science, and (6) either arts or another class in one of the prior 5 subject matter areas. Each course, whether SL or HL, requires both internal assessments (IAs) and year end testing scored outside the school (and country) — IB exams. HL classes usually try to spread the internal assessments across the two years, so students are not crammed up with deadlines senior year. For instance, the English oral exam may be in the spring of junior year for English HL, then the written paper in the fall, and then the 3 days of IB testing in May. In SL classes, the IAs happen in the same year of the class. Then there is the Extended Essay research project, and Theory of Knowledge and 2 years of Creativity/Action/Service.
In terms of scoring, each class can range from a high of 7 to a low of 0. The IAs, oral exams etc, all get factored into the score. It is not just the year-end testing that goes into that score. A student needs a minimum of 24 points to receive the diploma, and 12 of those points need to be from HL classes – basically, there is a minimum performance required for HL coursework. You could get a 6 in one HL and a 3 in 2 others, or a 4 in all 3 HL course, but the student must have 12 points in their HL coursework. There are also requirements about no scores being lower than a certain level to get the diploma. Then, a student can get up to an extra 3 points for ToK and the Extended Essay. Those are not easy points to come by.
The program is tough, but excellent preparation for college level work, both in terms of substance and time management. Students find out if they scored high enough to receive the diploma in early to mid-July after high school graduation, after college decisions have been made. The most selective colleges tend to give college credit only for 6s and 7s in HL classes; step down outside the top 20 universities, and you may get credit for 5s in HL classes, depending on the school. Keep shifting down the scale in terms of college competitiveness/selectivity, and you will find schools which give credit for 4s and also for SL classes. Some schools no longer give any college credit for AP or IB scores. Other schools may use test scores so that students can move into more advanced courses in a department, skipping the intro level, but do not give college credit for the test score received.
Bottom line – IB can be excellent training for college course work. If a student is counting on AP/IB credits to be able to graduate early etc., they should look at the colleges of interest to see what their policy is on test score credit, and consider signing up for AP exams as needed. It can be easier to get a 4 on an AP exam – often the minimum score required for 3 credits in college – than it is to get a 6 on an HL exam.