An organization may have associational standing to sue on behalf of its members when: (1) its members would otherwise have standing to sue in their own right; (2) the interests it seeks to protect are germane to the organization’s purpose; and (3) neither the claim asserted nor the relief requested requires the participation of individual members in the lawsuit. When an association’s structure does not allow for membership, the association may still have standing if the organization is sufficiently identified with and subject to the influence of those it seeks to represent as to have a ‘personal stake in the outcome of the controversy. Here, it was enough that the association was formed to promote the interests of teachers at the defendant’s schools who were exposed to toxic chemicals there. The close connection between the association’s mission and the interests of its non-member teachers is enough to give the organization a personal stake in the outcome of this lawsuit and thus associational standing to sue.