Professional testing firm PSI Services has acquired Software Secure Inc., a testing firm for grade and high schools and higher education, the companies announced Tuesday.

Terms of the deal between PSI, in Burbank, and Software Secure, in Newton Upper Falls, Mass., were not disclosed. It is the fourth acquisition in the past 12 months by PSI.

Chief Executive Steve Tapp said the acquisition supports PSI’s expansion in the academic market.

“By combining PSI’s extensive testing platform and operational expertise with Software Secure’s patented proctoring solutions and services, PSI is well-positioned to deliver world-class solutions and provide more choice to educators and learners now and in the future,” Tapp said in a prepared statement.

PSI’s services include licensing and certification tests, managerial assessments and pre-hire employment selection to corporations, federal and state government agencies, professional associations and certifying bodies.

Clients include national retailer Target Corp., Delta Air Lines, Department of Homeland Security, U.S. Postal Service, National Association of Legal Assistants and Center for Nursing, Education and Training.