Private School #4, Skeleton Key

TRAPPED LIKE A FLY-
IN A WEB OF MOUNTING TERROR
The aliens were taking over. At first, Jennifer thought the horrible menace was confined to posh Thaler Academy. But now, she and her friends were beginning to realize that no one could be trusted. Not even the police.
The terror was growing. The hideous creatures that roamed the school grounds assumed human forms.
And worse yet, the unearthly beasts knew about Jennifer and her plan to expose them. Could she stop the escalating nightmare before the aliens found the key to Earth's ultimate destruction?