A dispute over the federal agency charged with reviewing college accreditors may come to a boil at a key review session next month, when the waning Bush administration will have one of its highest-profile chances to try to force colleges to do more to demonstrate how well they help students learn. The federal agency is scheduled to assess five of the six main regional accreditation bodies and decide if they deserve renewed recognition. Some of the accreditors say the session has the potential to play out as a politically explosive showdown between the Education Department and the accreditors and colleges that have been seeking to take control of decisions about how institutions' performances are measured.