A writer has only a few pages to hook a reader. It doesn't matter if the rest of book is fascinating, page-turning reading if a reader can't get past the first two or three pages. If those beginning pages are weak, the readers will probably abandon the book. (Editors too, if your book is in the submission phase.) With TV, internet, cell phones, etc., there is too much competition for a young reader's time.
The writer has to reveal something to the reader. It could be a problem, a conflict or an attitude. It could be the emotional state of the main character.
Another approach is to present a question. Why does Nicole hate her father? What did Jason see his best friend do? What was that student doing hiding in the custodian's closet?
No matter what approach a writer takes, the result needs to be a beginning that hooks the reader.