Advantages and disadvantages of blocking software based on filtered ISP.

As internet-provider, I think that the best way to help parents who worry about their children viewing objectionable content is to install the blocking software based on the content-limited (or filtered) ISPs to control the content which is permitted to a reader. Am I right or there is another way? I would like to discuss the advantages and disadvantages of content-limited (or filtered) ISPs.
