The Soul Trade by E. E. Richardson

Corgi Books, 2009.
Searching desperately for a gift for his stepmother, Nick stumbles upon a shop in a unfrequented alleyway, called Bargains. Here he is intrigued with the array of glass orbs, and knows his step mother will like one. The sinister shopkeeper asks Nick for one of his drawings as payment for the orb, and Nick, without much thought, tears out a page in his sketch book and gives it to the man. Next day when at school in his favourite lesson, Art, he is despondent to find that he can no longer draw. His passion for art was leading him to find a place at an art school, and so devastated at the loss of his kills, seeks out the shop again to resolve what it happening to him.
But here he makes another bargain with the shop keeper: he will do some debt collecting work for him in exchange for his drawing and his skills. So Nick sets out on a perilous mission, one fraught with an ever present feeling of danger and fear. What he finds in recalling debts owed to the shopkeeper unsettles him even further as he is drawn into the world of Bargains.
A scary story sure to thrill those horror readers in your school: it will make them rethink the consequences of bargains.
Fran Knight