[I have 4 kids still at home, ages 4(when beginning with art instruction) to currently age 16.]
There is a good art program free on YouTube. The channel is called Let’s Make Art. They have a lot of follow-along tutorials for watercolor, some acrylics, and various other mediums. You can either provide your own materials and watch the videos free or purchase kits so you have everything you need. We have used these tutorials and also purchased the kits from them at different times. We always get good results, even from challenging projects.
We have also used Creating a Masterpiece and Sharon Hoeffer, the instructor is easy to follow and her teaching style encourages students to continue on in whichever medium they are studying.
Both of these art classes have helped us in our nature study drawing and have revealed art talent and great love for art in one of our children. These alone make doing art worthwhile.
Whichever art instruction you choose, please use good quality materials. The materials are crucial to the success of your students. They don’t need to be the most expensive products, but they should be good quality. Watercolor, charlcoal, or pencil are good places to begin since the materials tend to be less expensive.