Uncanny X-Men (1980) #151 FN/VF

The X-Men lose one of their own when Kitty's parents take her out of Xavier's School for the Gifted and enroll at the Massachusetts Academy. To make matters worse, the headmistress of the Academy is none other than Emma Frost, the White Queen of the Hellfire Club! Plus, the X-Men are taken off guard when a squad of mutant-hunting Sentinels shows up.