My son, a senior, is applying to selective schools with good CS departments such as CMU and MIT (as well as some safety schools). He has reached silver level in USACO, earned a 5 on the AP Computer Science exam, knows a half dozen programming languages, and worked part-time for a year as a programmer for a local tech company. I have talked to him about his projects at his job, and they sound non-trivial, for example extending a transpiler so that more of the code base at his company can be translated to JavaScript. He will get a recommendation from his supervisor at the company. He will try to get to the gold level at USACO this year.
What else can he do to make him stand out when applying to CS programs (other than good grades and test scores)? What should we ask his supervisor to emphasize in his recommendation? If he were to describe some projects he worked on the details would not be meaningful to an admissions officer who is not a programmer.