My take on this problem, from a while back:
<a href="http://short-sharp.blogspot.ca/2013/04/stop-white-board-coding.html" rel="nofollow">http://short-sharp.blogspot.ca/2013/04/stop-white-board-codi...</a><p>Summary: internships for junior jobs, code reviews for intermediate jobs, strength-of-record for senior jobs.