National Latin Exam.
It's definitely thorough, and at times you'll want to just pull your hair out. Sentence diagramming is "fun" enough in English, thankyouverymuch, but this curriculum demands you play that little game in Latin as well. There's no way your child can emerge from this program without a clear understanding of all the parts of speech and the mechanics of sentence-writing in both languages.
First Form Latin is available in a complete set, which includes a DVD lesson set, flash cards, teachers' manual, answer key and workbook. Heads up: you'll find it for less on the Rainbow Resource or CBD website than from the publisher. If possible, I'd strongly suggest a year the Latina Christiana or some other introductory course before delving into the First Form.