Larkhall Academy in South Lanarkshire is the first to implement the Informer system, devised by the Leicester-based Voice Connect company, which has been operating in more than 70 English secondaries in the past year.
The pound;5,000 system uses text and voice messages and e-mails, depending on parents' preference.
Tom Dingwall, Larkhall Academy's head, said: "With our new system, we are not only able to contact them all, we will be able to do so before lunchtime."
Alastair Campbell of Voice Connect said: "Parents are contacted within an hour or two if their child has failed to appear. They cannot slip through the net," Mr Campbell said.
The system can also be used to pass on news of parents' evenings and other events.