Understand grammar thoroughly. You should be able to spot grammatical errors, discuss grammar's meaning and rules and use grammar perfectly in your daily life. You can't teach children grammar without first understanding it yourself. It is essential that you have a solid knowledge of writing, reading, grammar and punctuation and that you can convey these elements to children.
Get some experience writing about grammar, sentence construction or children's education. Many publishers want to know that their authors have an education when writing educational books--especially for children. It is important that you have asserted yourself as someone who teaches writing or grammar, whether you're a teacher, education blogger or writer.
Research the market. According to the website Writing World, non-fiction children's writers should go to the library, book store and the internet to research books about children's grammar. Try to take a new angle with your book--this will give the editors something new and fresh to consider.
Write your book. A children's book should be written in a specific way, since children have shorter attention spans. Children's books should show and not tell (provide specific examples and reasons with pictures or sample sentences). Your voice should always be clear and concise, and you should eliminate any long-winded sentences.
Visit the "Colossal Directory of Children's Publishers Online," a website that helps authors find publishing houses and editors of children's books. For more comprehensive information, purchase the "2010 Writers Market" by Robert Lee Brewer. Look in the education directory of publishers and query the publishing house with your manuscript.