There is a solution to that too: Have the placement exam counted as a proficiency course in the student grades, like foreign language requirements or scientific prep courses in graduate-level schools for those majored in a different field.
They also don’t want to allow the advanced students to “test out” of the intro course, as some schools do, because the advanced students may be highly skilled at programming but totally lacking in introductory CS knowledge.
Source: Am a high school programmer