Save the Max - S2-E3
Factual error: When Zack is given the old newspaper with Mr. Belding's article, the headline reads, "Picture on pages 3 and 4." When he looks at the picture, he looks at the middle of the paper, with quite a few pages at both sides of the newspaper. Pages 3 and 4 would be near the front and would be on opposite sides of the same page.
Answer: As far as I can tell Jessie and Kelly decided to leave the show because their contracts were up and they wanted to pursue other things. But there were still episodes of Saved by the Bell left to tape so Tori came along to fill that void. Jessie and Kelly were supposedly still at Bayside, but they were "off-screen." The Graduation episode was filmed before Kelly and Jessie left the show.
ACertainShadeofGreen