How and Where Does Tori Come In?

Well friends, this question has been baffling me since my childhood, and I have just recently found the answer. Apparently, Elizabeth Berkley and Tiffani Amber Thiessen (Jessie and Kelly) decided to leave the show half way through the senior year season. As a result, Producer Peter Engel had to create a new character to fill in their spots. Jessie, Kelly, and Tori were supposedly all in the school at the same time, but in different classes. Therefore, they were never in any scenes together. The graduation episode was filmed before the girls decided to quit the show, so in the season finale, the graduation episode was aired.
Personally, I think this is ridiculous. I have been puzzled by this question for years and have had several debates about it. The producers should have informed the viewers of this travesty from the very beginning. You cannot just take out Zach's girlfriend/future fiancee and the class president for half of the senior year. Obsurd! Too many nights of lost sleep for nothing.
To see what really happened, take a look at this link!
http://homepage.mac.com/ijball/SbtB/history.html