When I first started in this profession, teaching science in a "hands on" manner was promoted as the best instructional strategy. The idea was to use manipulatives as often as possible because the more kids "do" science, the better their understanding of it.
Now that science is being held accountable via federal requirements, the hunt is on for what constitutes best instructional practices in science. The hands-on approach is starting to lose its luster, perhaps unfairly.
The most recent brouhaha has to do with a study conducted by the University of Pittsburgh and Carnegie Mellon Universtiay. "The study found that students taught through direct instruction were more likely on average to become 'experts' in designing scientific experiments." Furthermore, these students were also found to do just as well in applying their knowledge in the form of "analyzing and attempting to improve upon a series of science-fair posters...devised by other students." ("NCLB Could Alter Science Teaching"; Education Week; 11/10/2004)
Many districts and even one state (California) is looking at this information as proof that kids can do just as well without spending money for a bells and whistles kind of science program. Why worry about building labs? No labs means less need for equipment, safety factors, and you need fewer square feet per student (according to OSHA regulations). I can see why schools who are already pressed for pennies would find appeal in the idea of doing away with "hands on" science...especially if you can get the same results without it.
What I think groups are not looking at is simply the quality of the instruction. If you present an engaging curriculum to students (regardless of how you deliver it), students will actively participate. Meanwhile, not all students learn best in the same way. Of course you are going to have kids who gain more from direct instruction than from hands-on learning.
Science is not simply a collection of facts that you can present in the classroom alone. It is a way of knowing, and this requires practice. Some of this can be gained through classroom examples and discussion. Other proficiency is gained through the direct application of this information.
My forecast for future research is that it will show both hands on and direct instruction are necessary for student achievement. There is not going to be one "magic bullet." It seems as if educational research would be better served at identifying the best times to use each approach within the classroom. This would be far more helpful to teachers. Anyone looking for a project for a dissertation?