Midnight flight - V. C. Andrews

They lived on the wild side - now these bad girls are paying the price.
At Dr Foreman's School for Girls, the 'students' sleep in barns, work on a farm in the blazing heat, and are subjected to ruthless guards who watch their every move. It's an institution run by the dreadful Dr Foreman, a woman who delights in administering the worst form of punishment - the mysterious Ice Room where the girls face their darkest fears.
Now, Phoebe, Teal and Robin - three girls from very different worlds - are the newcomers in this desert hell. During their stay, each girl will be tempted to commit the ultimate crime of betrayal as Dr Foreman cleverly tries to turn them against each other - until they learn that the only way to survive is to stick together . . . and fight back.