Sure, we've got the usual box scratch paper, bins of broken crayons, mismatched sets of colored paper, watercolor sets with black mixed into the yellow, clogged glue bottles, and dried up glue sticks. The usual. But when we really want to do artwork, we get out the special stash of the good stuff.
We have a favorite series of eight drawing books for the younger set, called Draw • Write • Now. My kids have spent countless hours, pouring over these books until they are a tattered old pile. Yet they still love them. The books have fun, simple drawings that are interesting to children, broken down into a step-by-step process. Even young kids can reproduce some very good results.
Rather than using regular paper, we have nice but inexpensive drawing paper or rolls of butcher paper or newsprint and some nice drawing pencils. They really aren't expensive, but it's amazing how much harder they work and how much more seriously they take their own artistic efforts if it seems that you take it seriously enough to give them quality materials.
In middle school we have a favorite book we actually use in our homeschool. Discovering Great Artists by MaryAnn F. Kohl and Kim Solga is an ingenious work offers more than 150 art activities in a format that features a two-page spread for the best artists of history. It presents a bit of historical information about the artist, shows some of his/her works, and then provides an art activity that uses a similar style or technique the artist was known for.
This isn't some silly little course, it requires real art supplies of real quality. For years I've been purchasing my art materials from Dick Blick. Not only do they have great quality at very good prices, but they stock everything I need for the whole book, so I avoid searching all over town.
The first time we used this course years ago with my oldest, Jessica, we bought all the needed supplies. Monica, my fourth daughter is just beginning to use the course this fall. We are still using the same supplies and they will easily last through her two little brothers as well (assuming they don't sneak them away to be used as weapons in some army game).
One of our first homeschool purchases was the little, yellow Drawing Textbook. This book is a gem and easily teaches the basics of drawing, slowly building up one skill at a time. Each of my kids so far has enjoyed this book and really improved their drawing skills. And, of course, do gather some great drawing tools for your kids, too.
Art is an important piece of well-rounded education. For relatively little money, you can give your kids a great introduction.