The purpose of this lesson is specifically teaching the grade 1 class about plants and how they are living and requiring maintenance and care. It will also teach them a sense of responsibility for looking after something other than themselves.
I also chose this lesson because in the past when I have worked with children with autism, teachers or camp counselors feel the need to do everything for the child with autism. I would want to encourage the child to grow and become self-sufficient. Having them take care of their plant feeding it and keeping it in the sun will help them gain a sense of responsibility.