Retention can be improved by implementing a well thought out plan before the class starts. Have clear goals and easily understood expectation. I also wonder if it would be beneficial to allow the students to make choices so they feel more in control with the course. For example, if it is an English class, let the students choose topics for the papers.

We need to intervene early. Time is of the essence and if you wait too long it makes the situation worse.

In addition to providing efficient instructors, you need programs in place to assist struggling learners. There needs to be programs in place to assist students with additional academic needs.