As an instructor, what do you do if 1/2 of the class lacks the pre-requisites for the material. 'give them an F' sounds good. But that impacts a lot of people

As an instructor, what do you do if 1/2 of the class lacks the pre-requisites for the material. 'give them an F' sounds good. But that impacts a lot of people. What you need to do is move the material down a bit. Within reason.