President-elect Barack Obama named the head of the Chicago school system as education secretary on Tuesday and declared that failing to improve classroom instruction is morally unacceptable for our children.'' His choice, Arne Duncan, a longtime friend of Obama and a former professional basketball player in Australia who has a reputation as a reformer, called education the civil rights issue of our generation.'' Also Tuesday, Democratic sources familiar with the selection process said Obama has selected former Iowa Gov. Tom Vilsack as agriculture secretary. Obama will announce the appointment of Vilsack on Wednesday, according to the sources.