Some people have spoken about this topic previously, but I wanted to add my voice to the pile as extra weight. Just to clarify, I am only entering high school, but I am taking the Health and Medicine Course on Khan Academy to prepare for my future career in medicine (and also to keep my brain stimulated during summer in quarantine). Upon learning that several medical courses were being taken down, I was incredibly disappointed (along with many others). I have searched online to find a similar, in-depth, free course like this one, and couldn't find one up to par (although let me know in the comments if you would like to know to resources I found). The way these lessons are structured breaks down complex concepts in a way that is both thorough and easy to understand.  

I have seen in a few other comments that the YouTube videos in these courses will be kept on the Khan Academy YouTube channel, so it's not a total loss. That being said, there are several articles, quizzes, and tests along with the videos that are crucial for test prep and general studying (just to lock that information in your good old brain you know?) 

Anyways, I hope this comment and ones like it will be recognized by Khan Academy staff and that these invaluable resources will not be stripped away from me and many avid learners.