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Note cards are recommend since they don't crinkle or bend.   They're bound to get suspicious.
Write your notes on a piece of paper. Put your notes in your hoodie pocket. Sit behind someone so that your are obscured from the teacher's view. Try not to take too long; teachers likely notice who finishes last and especially if the student does surprisingly well given that it took them so long to complete it (for the excuse "I was being careful and taking my time" can only work so many times).