Take seriously the hands-on approach, because you will find that the common denominator between the math and the art is precision. Once students know that the shapes they are making are perfect in theory, they will strive to make them perfect on paper. Once familiar with the fundamentals, there's nothing to prevent taking the knowledge outdoors to landscape your yard and school grounds. Not only will you beautify the area, you will have built a mathematical resource. If you have two sticks and a rope you can duplicate everything you do with a compass and straightedge.
Students can design their ideas in class, testing their accuracy with protractors.
Outside, when the constructions are built on a much larger scale, you will find yourself using square root proportions to ensure the precision of the design. If you can make a circle, draw lines and connect dots, you can learn and teach a great deal about square roots, proportional constants, and irrational numbers. Instead of introducing these fearsome concepts as numerical abstractions, square roots are built into the shapes that you are constructing on paper during art class. To accomplish many of the designs, students will be working with square roots and other proportional constants without fear. Because the shapes are introduced as artistic exercises, without any kind of mathematical prerequisites, all mathematical content is optional and dispensed as you see fit.