New category of languages as `Classical Languages' was created by Government of India, and the following criteria were laid down to determine the eligibility of languages to be considered for classification as a `Classical Language':-
i) High antiquity of its early texts/recorded history over a period of 1500-2000 years.
ii) A body of ancient literature/texts, which is considered a valuable heritage by generations of speakers.
iii) The literary tradition be original and not borrowed from another speech community.
v) The classical language and literature being distinct from modern, there may also be a discontinuity between the classical language and its later forms or its offshoots.
Source : http://nganesan.blogspot.com/2008/11/classical-tag-for-dravidian-languages.html
Indian government announced Tamil as a Classical language. Then added Sanskrit. Now, on November 1st 2008 this respect has been given to Telugu and Kannada.