I have been teaching elementary art since 1973, and have experimented with several methods of teaching scratchboard. The best method I have used is at the third or fourth grade level, and involves wax crayons and india ink. The reason I teach the lesson to older kids than 2nd grade is they have better strength in thier hands and can put a thicker coating of wax on the paper. The concept is fairly simple: On a sheet of 9x12 tagboard, color many coatings of colored crayon ,
being careful not to leave any white paper showing. The coating must be very thick. I usually spend 2 art sessions doing this step. Use primarily light colors, such as pink, red, yellow, etc. Next, paint the paper with black india ink ( my favorite is Dick Blick Black Cat India Ink) starting with a small puddle in the middle and working your way out until all the ink is used up.Use a little soap if it won't spread, but don't over do it. Spread the ink in thin coats,
using left over wet stuff to go over already dry areas. Draw a picture on regular paper rather than drawing directly on the black ink and transfer the drawing by chalking the back of the picture. Etch the picture by using sharpened sticks or paper clips. When your budget allows, buy some scratch points, because they really produce excellent results.