What can be done to keep his sisters away from the television, especially the program "Star Academy"?

It is not permissible for a Muslim to approve a program that displays objectionable content in their home. Rather, they must change it with their hand; if unable, then with their tongue; and if unable, then with their heart, which is the weakest of faith. This is because approving objectionable content exposes everyone to God's punishment. One must strive to save their family from these objectionable acts through legitimate means, with gentleness.