Bobrowsky does a great job of explaining the problems around teaching students to do science with a hypothesis, so I won't break down each problem. But I do want to talk about how it leads us to more problems with the "scientific method." If hypotheses are misleading or confusing when we describe what scientists really do, the scientific method can seem like an outright lie.
So if we don't start with the hypothesis, I propose we start with observations. Science, at it's most basic level requires that we be good observers. And if we don't proceed with the scientific method, I propose that we simply follow our observations to the next discovery. UC Berkeley's Understanding Science site offers a way more dynamic explanation of how science really works.
Try using a tool like this interactive flow chart to introduce and explore the scientific process. As your students start making observations and identifying problems, you don't have to rely on some predetermined next step.
Of course, the scientific method isn't a lie, and it isn't entirely useless. It is a great tool for conveying the rigor of science and a way to separate scientific research from other forms of qualitative research or background research. The problem is that we don't use the scientific method that way; more often we use it as a prescription for the scientific process, as if every project goes through the same steps. When is the scientific method useful? I find that it is most helpful in determining the rigor and scope of a project. I use the scientific method as a sort of check list to make sure that my work will be understandable by others and reproducible.
What do science projects look like in your classroom?
How do hypotheses and the scientific method help or hurt the process?