A picture is worth a thousand words. If that works for you (or your student) you’ll love this free introduction to geometry first published in the late 1800s: Marks’ First Lessons in Geometry by Bernhard Marks.
The author holds that this science should be taught in all primary and grammar schools, for the same reasons that apply to all other branches. One of these reasons will be stated here, because it is not sufficiently recognized even by teachers. It is this:—
The prime object of school instruction is to place in the hands of the pupil the means of continuing his studies without aid after he leaves school. The man who is not a student of some part of God’s works cannot be said to live a rational life. It is the proper business of the school to do for each branch of science exactly what is done for reading.
Children are taught to read, not for the sake of what is contained in their readers, but that they may be able to read all through life, and thereby fulfil one of the requirements of civilized society. So, enough of each branch of science should be taught to enable the pupil to pursue it after leaving school.
If this view is correct, it is wrong to allow a pupil to reach the age of fourteen years without knowing even the alphabet of Geometry. He should be taught at least how to read it.
In this geometry book, the student is to be occupied with the drawings, not the text. So for example, the first lessons focus on naming the lines in Diagram 1 and learning about the characteristics of those lines. Basic geometry.
In this manner, the student learns about the various types of lines (horizontal, vertical, etc.), angles (acute, obtuse, etc.), polygons, triangles, quadrilaterals, circles, and so forth until he progresses to measurement. Each lesson builds on the last.
Axioms and theorems are included at the end after the student has an understanding of basic geometry. Review questions are available at the end of every chapter. Test questions are also included.
This is the type of book every student should work through! It is rich in its simplicity and will very adequately lay the foundation for any future math studies — formal or otherwise.