E.M.
There is a big difference between how you teach a kid with real ADD/ADHD not to interrupt and how you teach a kid without ADD/ADHD not to interrupt. If he really is ADD/ADHD, typical techniques are not going to work with him--like consequences, teaching him with the "How do you like it when I do it to you?" method, etc. because it is a matter of impulse control --not a matter of bad manners--two very different things. Your best bet would be to google other symptoms of ADD/ADHD to see if anything else fits because how you handle it will vary greatly as well as your results. As the adult woman with ADD said, it is still hard for her at 30. Her family has learned to be tolerant and forgiving. Lots of kids with ADD/ADHD are smart--and even gifted, so being smart and having ADHD is not rare. If he is truly undiagnosed and living with ADHD, think how frustrating it must be for him to live in a world where you are expected to wait calmly, sit and be still and listen without talking when his brain is not wired to do those things naturally. I have an ADHD husband and daughter (both unmedicated as of yet) so I am quite familiar with the frustration of being interrupted but I have also learned to have patience and tolerance for those who behave in ways that "typical" people find challenging.