<p>MIT does not have an official extension program, although I know people who have enrolled in MIT classes as special students while in high school. It’s up to you to work it out with your eventual college as to whether you’ll just get credit or whether you’ll have to do something else.</p>
<p>Several of them ended up coming to MIT for college with varying degrees of credit transfer. One of my friends had to retake some of the math classes (he did very well, obviously) because MIT had no official record of him taking them as a student in order to get credit.</p>