Currently I'm finishing up my B.S. in Adult Education, which required 2 internship stints (did one with S.D.P.D. and the other with a local college). I'm starting grad school in the fall, which also requires 3 internships (1 a year long with a local high school district and 2 more next year, one with a middle school and the other an elementary school, I'm going for a M.A. in Counseling)

Most people don't realize that there's multiple sources of funding for these internships, thus some pay more than others, even for the same job. For instance, for my fall internship I'm going to be on a team of 4 people, but I (a woman) will be making more than the other 3 (2 women and a man) because the source of the funding for my position (team leader) is different than the other 3. My grad school could only pay for 3 of the internship positions and the max they can pay is $7.50 an hour. However, the high school district can pay up to $11.50 an hour for a "casual worker" position. Since I'm the team leader and I was chosen for the higher pay. We'll all be doing the same job, basically, but the origin of funds differed.

So, I would ask what program his internship was under and if they have different schools. When I worked with the police, half my pay came from the city training funds, the other half from my school. The amount per student received is often set by the regents, and that, rather than gender, is likely what is causing the pay discrepancy. There are also other programs, such as in California the CalWorks program, which supplements income for those who are on welfare but working towards becoming self sufficient. If he is a single dad, or he and his wife earn below the poverty line combined, then they would qualify for subsidized employment. This is usually only a dollar or two more, which again would make up the difference here.

Finally, as others pointed out, he may have simply bargained better when applying. Often with internships you negotiate the terms, much like a regular job. Some people simply settle for less than others. Regardless, her internship already looks successful, as she's getting an education in how the real world works.