Withdrawing children from public school in Missouri is really quite an easy process. The problem is that many public schools are going to give you the run around and tell you things that aren’t true because THEY don’t know Missouri’s homeschool laws. Before you withdraw a child be sure to familiarize yourself with Missouri Homeschool laws. It will make it easier on you if the try and pull a bluff. Fortunately, not all people who work in the public school try and make it difficult, some are very accomodating.
In 1990, the law was modified to require parents who wish to remove five and six-year-old children from a public school setting to do so in writing. Again, this is merely a notification, not a request of permission. -Families for Home Education
The following link provided by FHE is a wonderful sample letter for public school withdrawal. I would recommend this letter to be sent when withdrawing children of any just to prevent any truancy reports.
Sample notice of intent: http://www.fhe-mo.org/sampleletter.pdf