To begin with, HSTP purports to put curiosity back at the core of science. The classroom is at once the activity room. The laboratory is not separated from instruction. All concepts are brought out by performing experiments. Students formulate the outcome of the experiments in their own language. The process of science in practice has almost always involved a practical exploration of the phenomena, often out of sheer curiosity. Thus the program re-establishes the link of knowledge directly to ones own explorations. And this to my mind is the most outstanding ingredient of this program.
But curious explorations have no explicit goal to direct them. They are lengthy and time consuming. So this can clearly not be a strategy for mass education. The compromise is to have what is called "guided discovery". As such the HSTP text books are more correctly science workbooks. They begin with a brief preamble to the subject. Then they proceed to give step by step instructions for activity, punctuated by questions to be discussed by the group and by tables for recording observations.
Who performs the experiment? Demonstration experiments are a well developed educational tool. But nothing is more valuable than doing the experiment oneself. HSTP lives by a motto derived from an ancient Chinese proverb "I heard about it and I forgot/ I saw it and it stuck in my mind/ I did it myself and I understood it!" The practical implementation of this is that experiments are done in groups of four or five, often with sufficient equipment that several members of the same group can simultaneously do it with each others' help. The teacher has to circulate in the class, aiding with the method of setting up and observing.
The teacher's role is manifold and challenging. He or she has to begin the class with getting the children to give some examples of the subject matter from their daily lives. Interest has to be generated for taking up the experiments. However, neither the outcome of the experiments, nor the conclusions are to be told - neither at the beginning nor at the end! The observations will of course be done independently, then they will be shared with the whole class. Often, a member of each group comes to the blackboard and enters the results of his or her group in a common table. The conclusion about the phenomenon studied will have to emerge through discussion and a set of "leading questions". By and large, after some discussion, a few in the class will latch on to what is really happening and then they will state it in their own words. If this doesn't happen, more hints have to be provided. The real demand on the teacher is to weather erroneous conclusions often resulting from wrong observations.