I think California is the only state to have this type of test (and even most Californians don't know it exists). OP isn't talking about the exit exam, which students must pass in addition to taking the courses. This test is a different one. When I used the California State High School Proficiency Exam to leave high school at 15 I got a certificate that said that it was the legal equivalent of a diploma. It may or may not be recognized in every state, but once I had my BA, no one cared about that anymore.
From their website:
"All persons and institutions subject to California law that require a high school diploma for any purpose must accept the certificate as satisfying the requirement."
About the Test - California High School Proficiency Examination (CHSPE)
Oops - OP asked about how it's seen in social settings. I think this depends on whether those in that setting are aware of this test, and whether or not the person continued on to college.