[eloisant]

It's like with the justice system: if you have to choose between the risk of jailing an innocent and the risk letting a guilty person go free, you choose to let a guilty person go free. All the time.

Unless you're 100% sure that a student cheated, you don't punish them. And you don't ask them to prove they're innocent.

[array_key_first]

It's extremely reasonable to ask student to show their work because tests are testing understanding. The understanding IS the work.