Undergraduates benefit as well. Because they are responsible for designing and implementing specific science activities, they gain an appreciation for how much science they know by testing their capabilities. Undergraduates are required to apply what they know in order to answer students' questions. If undergraduates are mentored by a faculty member, they can gain valuable training to improve their teaching skills. They might also get academic credit for these activities.
Undergraduates also know that they have a positive influence on the middle school students.
This experience can open doors for them and encourage them to think about teaching careers. In general, teachers and administrators of school systems are eager to have the kind of contact with a college that science clubs engender. Using existing connections is probably the easiest way to start a process like this. If a college has run professional development workshops, contacting teachers who have been involved in those workshops is a potential avenue for working with the schools. Clearly it is important that support for the program come from all levels at both the school and college in order to solve any problems that may arise and to help sustain the program.