The University of Phoenix, the nation’s largest for-profit university, is closing 115 of its brick-and-mortar locations, including 25 main campuses and 90 smaller satellite learning centers. The closings will affect some 13,000 students, about 4 percent of its student body of 328,000.

It is also laying off about 800 employees out of a staff of 17,000, according to Mark Brenner, senior vice president for communications at the Apollo Group, which owns the university.

After the closings, which are to be completed next year, the University of Phoenix will be left with a nationwide network of 112 locations and a physical presence in 36 states, the District of Columbia and Puerto Rico.

Apollo stock closed Wednesday at $21.40, down $6.09, a 22 percent decline.

Enrollments at the University of Phoenix and in the for-profit sector over all have been declining in the last two years, partly because of growing competition from other online providers, including nonprofit and public universities, and a steady drumroll of negative publicity about the sector’s recruiting abuses, low graduation rates and high default rates.