Two major players in the school textbook industry will join forces under an agreement announced Friday in which Houghton Mifflin Co. will buy Evanston-based McDougal, Littell & Co. for $138 million.

Boston-based Houghton Mifflin is a major publisher of textbooks and other educational materials, primarily for elementary schools. McDougal is largely a supplier to middle and high schools.

Houghton Mifflin said McDougal Littel will run the company's secondary-school book publishing division and will remain based in the Chicago area.