[Synesthesia]

The Taker by J.M. Steele. It's about a senior named Carly Biels who tanks the SATs. Soon after getting her scores, she receives a text from a person called the Taker, who says he will retake the SATs for her and get a score within 150 points of perfect, but for a price. She agrees and tries not to think of what will happen if she's caught, but she also takes tutoring with a nerd called Ronald Gross (rhymes with "floss") so it won't look suspicious when her score goes up by so much. To make things worse, one of her best friends Jen is conducting a huge investigation on who the Taker is and who he has helped.

It's a really good and interesting story and the ending is ADORABLE. I totally predicted the Taker's identity AND his motives correctly. xDD