With 12% Unemployment, Why are These Jobs Still Vacant?

The Las Vegas Valley has about a 12% unemployment rate but some jobs go begging.
For instance, the Clark County School District is begging for school bus drivers.  It is so bad that there are days when some routes are not covered and the transportation department scrambles to find drivers to cover the routes and sometimes they "accidentally" forget to send a driver to school and then everyone scrambles to find rides home for the kids.  The hardest area hit is the special education buses.
Here is a link of non-licensed openings in the school district:  http://www.ccsd.net/employees/prospective/opportunities/support-staff/
Further, these are fairly good paying jobs, good benefits and you get health insurance.
And yet, people complain they cannot find jobs.
I call Bull Crap!.