For the last three summers I have run a small program to bring high-school students from underrepresented minority groups to my university for four weeks during the summer to take a course and work in my lab. All of these students have come from highly-underperforming school districts and have done really well and have been admitted into very good colleges. This program is the result of my "broader impacts" section of an NSF award I have, and I encourage other people to propose such programs when writing their grants (if you need some advice on designing such a program contact me). My university also runs a much larger program for undergraduates from underrepresented minority groups to do research during the summer in top labs throughout the country. Again this provides a great opportunity to a group of good students. I think these programs are laudable for their goal of trying to increase diversity in the sciences and for giving students from underrepresented groups a chance that they might not normally have.
For the most part, in these programs the definition of enhancing diversity in sciences and other academic fields means increasing participation of minorities (and women) within the sciences. However, I've started to think that this is a somewhat narrow view of what diversity should mean. In my view, the current rationale for providing programs to help minority students is that these students traditionally don't have access to the same type of educational resources as non-minorities do. This is due in part to the fact that many come from socioeconomically disadvantaged areas which simply do not have the same resources and academic support networks. Yet, there are several other people who also do not have access to these resources because they also come from socioeconomically disadvantaged areas, but just not happen to be from an underrepresented racial or ethnic minority group. I think it would make a lot of sense to expand our definition of diversity to include socioeconomic diversity, since this would be a way to reach a larger group of folks, rather than just using race or ethnicity as a criteria to define who is an "underrepresented group".
Let me give you an example. I do a fair bit of advising to undergraduates at my institution, both first-years and sophomores as well as ones majoring in my discipline. Many of them are first generation college students, meaning that they are the first in their family to go to college. Since this is a private university, the socioeconomic disparities between students can be huge, and some of these first generation college students have expressed concern that there is no support network for them. My university has gone through great lengths to establish mentoring, support and affinity groups for minority students, but nothing for these first generation students, who although they are not minorities, they have a lot more in common in therms of the college experience with the minority groups than with other non-minorities on campus. Some have mentioned that they have forgone the chance to do research over the summer because they cannot afford it and there are only a few special fellowship programs they can apply for. Likewise, volunteering in a lab during the semester is not an option because they need to use their spare time to work. This would over time limit the representation of this group in the sciences, and obviously they could benefit from more widely available programs.
Expanding the definition of diversity to include socioeconomic diversity is not as simple as it sounds. While it is relatively straightforward to assess racial or ethnic diversity in a given academic field, how do you asses socioeconomic diversity? Do you ask people their income? Presumably by the time someone gets a job, the socioeconomic discrepancies start to become less evident. So it is important to do this at the high-school and college levels, where opportunities can be provided to people who could benefit from them but who do not fit into the typical categories of an underrepresented minority.