I’m also assuming, as suggested in the comments, that the “worst case” implies the need for calculators. How many times have we had to see calculators, or both?

If that is case, I believe your original choice of the semicolon is appropriate, since it is intended to link two closely related independent clauses (which is what are you currently using).

What to do when the worst happens?

I

don’t want to use a calculator during the day. I can’t figure it. I can’t use a calculator in a math class.

What are your opinion on these items?