Make sure that your child is wearing respectable and clean clothing. Check, however, to ensure that your child feels comfortable being himself in the clothing. Let him wear the outfit for an hour or two in advance to ensure that he is not scratching himself awkwardly or squirming in his seat when he wears it.
Help your child learn how to sit still for a long period of time. Interviews can be tedious for children, and interviewers will be checking to see how your child deals with sitting for a long time. A child who is moving around in his seat a lot or becomes easily distracted may set off a red flag as a child who will not be able to attend in class.
Give your child the communication tools he will need at the interview. Explain to him that if he doesn't understand the question, he can always ask the interviewer to clarify. Help him practice using phrases such as: "I'm sorry, can you explain what you mean by that?" or "Did you mean X or Y?" to do so. Make sure that he understands how to introduce himself to the interviewer politely, as well as how to thank the interviewer at the end.
Encourage your child to be honest, yet polite, about his opinions and experiences. Tackle any difficult questions that might pertain specifically to your child's situation, such as "What will you say if the interviewer asks you why you didn't want to be home-schooled this year?" or "The interviewer will probably ask you about how it feels to be considering switching schools. What do you think you'll answer?" Make sure, however, that you don't feed him the answers to these questions; instead, asking him the questions now should encourage him to think more deeply about how he will answer them.