While the College Board plans to unveil a sweeping revision to Advanced Placement biology courses on Tuesday, it is delaying similar changes in United States history by a year to address concerns from high school teachers.

The changes in both subjects are part of a broad revamping of A.P. courses and exams to reduce memorization and to foster analytic thinking. But while the new biology curriculum is specific about what material needs to be covered, some teachers complained that parts of the history course seemed vague, and the board said it needed more time to clarify what should be studied.

Board officials said they expected to publish the new United States history curriculum next