One of the possible projects on the Danga Summer of Code page is a searchable system for finding people who attended a particular school. I guess the idea here is to try to ape sites like Friends Reunited, but with a reason to actually stay on the site once you've found someone else.
The first thing that springs to mind is that it's far too specific. There are lots of other things people might want to search by, such as people who worked at the same company, or people who like pizza. We already have a grouping system on LiveJournal via communities, but communities are hard to find and there are often many of them about a given topic. I think, therefore, we can build apon this idea to make a general system that would unite interests and schools/workplaces attended and perhaps even the nutty LiveJournal Singles into one idea.
The idea is to create a heirarchical journal directory, similar to the old topic directory but applied to finding journals rather than to entries. Users and communities would be able to list themselves in the directory in various places. There could also be “magic” categories for people who list a given interest, or are of a given age, though of course people could opt out by choosing not to be listed in the directory using the already-provided option. Allow communities to also be listed in categories and you've got yourself a community browser.
With this in place, it's just a matter of providing an interface to show people who are in a particular category to provide such things as a school search. The remaining concern then is how the list should be managed. An ad-hoc method where people can create categories anywhere will likely end up with chaos, so there needs to be some enforced structure somehow. When it comes to schools, they should most probably use a heirarchy like Country/Region/Town/Type/Name/Year of attendance. People would have to be able to submit new schools, of course, and jokers would probably end up submitting fake schools, but at least the real ones will be arranged in a manner so that people can actually find them.