As awareness increases that sign language can help young hearing children to develop their English skills, more parents are teaching ASL to their hearing children that are homeschooled.
An example of this was found on the now defunct Homeschooling Preschoolers and Early Elementary web site. On this page, a parent wrote about teaching ASL to homeschooled children. According to this page, one reason it made sense to teach ASL to homeschooled children is because ASL's grammar is closely related to the way young children speak. A web search turned up one parent's "daily routine" page for homeschooling their preschooler, which included sign language practice, learning a new sign each day.
Some homeschooling support groups offer sign language classes in addition to field trips and other group activities. Homeschoolers can take advantage of the many available sign language learning materials (video, web). Homeschooling sign language lessons are also available, such as Hands On Sign Language.
Finally, the long-established NATHAAN (National Challenged Homeschoolers Associated Network) maintains a lending library that includes sign language materials.

