IB credits can be VERY useful. At many colleges, students who enter with enough of them may be allowed to “accelerate” and graduate early (a big money saver!). IB credits may also allow students to skip introductory classes. (But be wary. Some students find these intro classes boring, yet others who have jumped ahead … especially in technical fields like engineering … have later complained that they weren’t adequately prepared by their IB program.)
Note, however, that colleges … even similar seeming ones … may have markedly different policies when it comes to IB credits. Not only will these policies vary from college to college but sometimes even from department to department within the same institution. So you have to read Web sites carefully to see what exam scores you need in order to earn ANY credit and also to find out exactly how this credit can be applied. Note also that these policies might even vary from year to year, so don’t rely on the grapevine for information.
Most (but not ALL) colleges will award some sort of credit for strong performance on the IB exams, and all (as far as I know) will at least use IB results for placement purposes.
When it comes to earning college credit before actually enrolling in college, IB and Advanced Placement exams are the most reliable. Summer classes and other courses taken during high school may or may not provide you with credits that the college you choose will accept, no matter what you were promised when you signed up for them. But never assume that the IB credits you can earn at one college on your list will be the same at the next. In fact, you may feel as if you need a college degree (preferably one from MIT or Cal Tech 😉 ) to discern the differences!