We interview for our summer interns every year.  They are college/grad school age and must have had some previous experience working with kids (beyond babysitting). 

To help us narrow the field of applicants we have them actually complete a short job application beyond just the resume and cover letter. So, they get some questions in advance.  Applicants who expounded at great length on their applications about having a ton of experience with kids turn out to completely bomb that portion of the in-person interview and have merely watched their nephew for a few hours while their sister went shopping. 

I'm with you in the need for spontaneity and knowing how well someone thinks on their feet. In our profession it can make all the difference.  As for inclusivity, we have more of an issue getting applications from people of color, but the applications we do receive have resulted in some wonderful interns.  This year we went to our local university's employment fair and gave out info on the internship.  We had more applicants of color. We had our first "known" gender non-conforming applicant (they introduced themselves to us that way, we don't ask).  And, we got to speak to many of the applicants before we ever decided who to interview. 

We will probably go back to the university job fair next year because it worked out well. 

 
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