Jackson had outstanding grades, and academic credentials, but she did not have any family contacts, so the best clerkship she could get was a Federal District Court. That was good, but not great. She worked hard, did great work, and...
...WAIT FOR IT...
She was able to get the judge she was clerking for to recommend her for a better clerkship. It is rare, but lawyers can sometimes use one clerkship to get a better clerkship. She needed the judge she had to convince another judge that she was a really great clerk. Worth mentioning that the judge needs to push people with family connections out of the way to get her in, so she had to be very good to get this. So she was a clerk to a Federal Appeals Court judge. That is great, but not fantastic. She worked hard, did great work, and...
...WAIT FOR IT...
I have never heard of anyone being able to get three clerkships, being able to do two jumps. Doing one jump was rare enough, but two just does not seem possible. Jackson's hard work and excellence paid off, and she got a clerkship with the Supreme Court. There is nothing higher than that.
@T. A. Gardner