Starting in the Logic Stage, which is grades 5-8, you will want to teach the child to outline. The Well-Trained Mind explains why a slow progression of this is best as it prepares the child for high school. Don't make it any more complicated than you should, it really is quite simple!
5th Grade - Begin to teach the child to outline once a week. Explain that outlining is simply finding the main point (summary) in the paragraph. You will want to choose a text from that week's history resources that the child read about the topic they found most interesting. You will start using a text that contains 5-6 paragraphs, or one page. Have the child take each paragraph, one at a time, and find the main point by answering the question, "What is the main thing or person and why is it or are they important?"
Example of one-level outline:
I. Main point of 1st paragraph
II. Main point of 2nd paragraph
III. Main point of 3rd paragraph
6th Grade - Same as before but you add in subpoints under each main point, which are lettered A, B and so forth. Use 2-4 subpoints under each main point it relates to. Outline up to two pages. To find the subpoints, simply write the additional information given that correlates with the main point.
Example of two-level outline:
I. Main point of 1st paragraph
A. First supporting point
B. Second supporting point
II. Main point of 2nd paragraph
A. First supporting point
B. Second supporting point
C. Third supporting point
7th Grade - Same as before and when the child has got down the two-level outline well, you can start adding in more supporting points. These points are numbers (1, 2, etc.) that give details for the letters (A, B, etc.). If the child isn't ready, they can hold off until the start of 8th grade. Now the child outlines 2-3 pages.
Example of three-level outline:
I. Main point of 1st paragraph
A. First supporting point
1. First subpoint
2. Second subpoint
B. Second supporting point
1. First subpoint
2. Second subpoint
II. Main point of 2nd paragraph
8th Grade - Same as before but now outlining 3-4 pages and doing three-level outlines.
Example of three-level outline that sums it all up:
I. Main point
A. Additional information about the main point.
1. Detail about that additional information
In The Well-Trained Mind, she states a simple question the child can ask themselves as they write the outline for supporting points - "What else is important to know in this paragraph?" You can read the whole section on how to outline in the book on pages 297-301.