The Inquiry Struggle

I have used inquiry-based units in my social studies classes. Some have been online (e.g. a Webquest about Antarctic exploration) and some have been in the classroom. The problem with of them has been that the students have had difficulty breaking away from their previous expectations. They constantly ask if what they're doing is right or if their answers are sufficient. The toughest part to me about the inquiry model is asking the right type of questions and keeping a balance between their freedom to explore and making sure they are accomplishing the tasks at hand (within the allotted time). Most of the time, I provide the (pre-filtered) research materials. This has allowed them to access a variety of material and still stay within the bounds of the project itself. The toughest part about inquiry-based units is the preparation and the amount of time they take. It's definitely an issue of quality over quantity. Sadly, my curriculum doesn't really see it that way.