Question on PSAT packet: What Religion are you?

My son, a 10 th grader at Newsome told me that on the packet for the PSAT there was this  question:  "WHAT RELIGION ARE YOU?" and listed several choices.  Please explain to me what that has to do with the practice SAT?   As a Christian, I know that any mention of God or faith seems to be squashed in the public schools -so why this question is acceptable on a public school test is strange.  Why are they asking this information?  Anyone else's student mention this?