Can't remember quite how old I was (I'm thinking probably around 10-12 yrs. old) at the time when I started questioning whether or not Santa was real. But when I did start questioning, my dad sat down and read a book with me. Can't remember the exact book, but it it asked the question...Santa are you for real? As I remember, it told the story of the true Santa Claus - St. Nick, and then as the story ended, it left it open for imagination. I remember that after reading the story, I understood that St. Nick was REAL back in the day, but then I still kind of questioned whether or not Santa was still real today - made me know in my mind that he was truely not real, but the idea of him was, and then again I didn't NOT want to believe because it was fun...
As I said, I don't know the exact book that my parents gave to me, but I found one online called "Santa Are You for Real" & it sounds pretty similar; here's a review link ==>
http://www.commonsensemedia.org/book-reviews/Santa-Are-Yo...
Then to top it all off, after leaving the story to rattle my brain, either that same year or the year after, my parents arranged for us kids to see Santa at work leaving gifts under our Christmas tree. Late Christmas Eve night just arriving home from midnight church services, we pulled up in our car to our house to see Santa Claus all decked out in his suit inside our front room with all the lights on & leaving gifts. By the time we all pilled out of the car and opened the front door, he was gone...we were amazed at how fast he flew up our chimney & dashed off our roof! (Years later to find out that it was really a family friend in costume & he really dashed out the back door to his car around the block!) But it was a memorable Christmas that year, and made me realize that no matter what my friends thought...I would always believe in the fun and imagination of Santa & Christmas.
And I hope to pass on a similar story book & spectical for my young daughter when she gets to the age of questioning.
Good luck to you...