Read a post to the Usenet newsgroup soc.culture.tamil for another person's perspective. If carried out, this policy is very beneficial. If a child must speak in English, translate the sentence to Thamil and require that it be repeated. This activity will connect the children to their relatives as well as offer a meaningful opportunity to practice their language skills. Thamil songs and radio stations are readily available on the Internet.
Immersion is the best way to learn language.
This suggestion is directed mainly at those individuals who spend time volunteering in high school and college. Consider helping other people, building your resume, AND improving your Thamil skills at the same time. Volunteer in a place where you will be immersed in Thamil. So far, I don't have many resources for this, but here's one that seems promising. Page first and last updated on May 16, 1998.