If you are the cooperating teacher hosting a student teacher, please be honest with the college supervisor. Don't think that you are failing the student teacher if you hide their shortcomings. There may be options that we should consider. In an extreme situation, we may need to change her placement. We may need to terminate the placement and try again next semester.
But there could just be a need for intervention and reteaching. Just like you intervene when you discover needs in your elementary or secondary students, we might need to do that with a college senior. These are very young adults, and it is our job to teach and encourage them to make the changes necessary for improvement. Let's work together to develop them to be the best possible educators of children.
Give them things to improve.
When I say that the student teacher should sink or swim, I do not mean that they are left out on a limb by themselves. You, mentor, are not just watching the student teacher. You are not just an example to him. Just like you identify deficiencies in your regular students, you should be finding them for your college colleague. Identify those things and help them fix those things. Take him from where he is to the next level, wherever that may be.
Praise them. Acknowledge success. Acknowledge progress.
Your student teachers are entering a noble, and sometimes thankless, profession. That has to be worth something. They may not be the best at what they are wanting to do, but they're also rookies. They haven't regularly led a classroom of their own, and the bottom line is they still aren't in their own classroom. You still own the class they are trying to lead. Encourage them daily, but don't just hand out empty comments.
You're doing fine.
Tomorrow will go better for you.
I appreciate your effort.
Good job.