If I close accounts can I raise my credit score

Is it true that if I close out accounts which have been paid in full that my credit score will go down? I was told by a local bank just that. I have several accounts which I have paid in full and I am afraid to close them out. My present credit score is 797, which is not bad, but I would love to have it jump to 850 if I can. Please advise how I can accomplish my goal.

Thank you,

Live human being
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Bo Majors / to Perfect credit score and wants it better / May 10
It is somewhat embarrassing to answer questions from a 797.
Find some other project as this one is not in need of tending.