We had preferred but couldn't file a lawsuit because no boy presented himself as a plaintiff for admission to the Young Women's Leadership School.
Commenters were wondering about the meaning of "preferred". It could be a typo for "prepared", or a grammatical error in saying that they preferred to file a lawsuit. But "prefer" also seems to have a technical legal meaning, e.g. Wiktionary has "To present or submit (something) to an authority (now usually in 'to prefer charges')". However, that would seem at first glance to correspond to filing the lawsuit, which is just what the author said they could not do. So maybe there are separate steps involved?
Can someone explain what is probably meant by this passage? What specific steps toward a lawsuit is the author saying that the plaintiffs took, and which steps were they unable to take?
The article's author is a lawyer, so I would assume by default that they are familiar with the terms, and that the usage is deliberate instead of a mistake. The lawsuit in question would have been in US federal court.