My son and I did this Watercolor Line Art activity over the summer; it was a great way to share some one-on-one time while having fun exploring a fun paint medium and a way to sneak in some math concepts.
post may contain affiliate links.
Math and Art Activity
Simply use the ruler to draw lines-- parallel lines, diagonal lines, vertical lines, horizontal lines, perpendicular lines, short lines, long lines, etc. etc.-- all over the paper.
We just drew lines wherever we chose, but this activity would also be neat with specific tasks, i.e. draw a line 5 inches, draw a vertical line,... and see what design you come up with!
Also, encourage your student to push a little bit harder than normal while drawing the lines so that they are darker.