There have been multiple threads on this topic already:
http://talk.qa.collegeconfidential.com/parents-forum/2004504-test-optional.html
http://talk.qa.collegeconfidential.com/sat-act-tests-test-preparation/2183088-test-optional-admission-what-you-need-to-know-right-now.html
http://talk.qa.collegeconfidential.com/college-admissions/2189411-test-optional-what-does-will-not-be-disadvantaged-mean.html