Reinforce the idea that a student's results are not wrong just because they are different from a classmate's results. After all, chemistry is all around us, not just in the chemistry lab. When interacting with students, take care to involve all of them. It is very worthwhile to spend time talking informally with small groups or individual students before, during, or after your presentation. It is important to convey the message that chemistry is for all who are willing to apply themselves to the questions before them.
Chemistry is neither sexist, racist, nor frightening.
For more information on becoming involved in the classroom and a practical and valuable discussion of some do's and don'ts, a resource is available. The American Chemical Society Education Division has an informative booklet and video called Chemists in the Classroom. All rights reserved.