Students can create some very complex ideas just using the edge of
corrugated cardboard dipped in ink. You can add to it card board
cylinder sections for curved shapes (like cut up empty masking tape
rolls). Be sure to check the student art gallery.
You might try using acrylic paint as ink so that it will be water
resistant when dry. Students can then paint their compositions with
water colors.
Quite striking was white ink on black paper - then colored with
construction paper crayons, pastels or oil pastels.
I will add this to the printmaking ideas for elementary.