I seem to remember coming across an educationLevel delimited search results page
that had one or two results, but I can't seem to reproduce that. I might have
been mistaken when I filed this, will update the issue if I can find an example.
But right now it appears to be returning zero results.

Do some examples return "few" results?  The title makes it sound like some cases
return fewer than expected results; an example of that would be helpful as well.

For example, the search "physics"
(http://discovered.creativecommons.org/search/search.jsp?lang=en&query=physics)
returns around 5k results, many with educationLevel:Learner, but when you
delimit the search to that level
(http://discovered.creativecommons.org/search/search.jsp?query=physics+educationLevel%3A%22Learner%22),
you get zero results.