Secret Bodyguard (1991)

Mr. Belmont is a rich man who cannot control his teenage daughter Tiffany. She rebels against her father and decides to attend the local public high school so she can be with people her own age. Mr. Belmont accepts, but in secret, however, he hires Ernie, a young martial-arts fighter, to be Tiffany's friend and bodyguard. There's only one catch: she never must know it.