Aps-ajp-11-1001-Book indb

I. DESIGN PRINCIPLES
The fi rst design principle is that learning builds on prior 
knowledge. Prior knowledge may come in the form of experi-
ences and intuitions as well as ideas (both correct and incor-
rect) that were previously learned in formal education settings. 
Incorrect prior knowledge is often strongly held and resistant 
to change, but it also has valuable aspects that can serve as 
resources for further learning.
Each activity in PET consists of four sections: Purpose, 
Initial Ideas, Collecting and Interpreting Evidence, and 
Summarizing Questions. The Purpose section places the 
material to be introduced in the context of what students have 
learned before, while the Initial Ideas section is designed to 
elicit students’ prior knowledge about the central issue of 
the activity. Both within the small groups and in the whole-
class discussion that follows, students usually suggest ideas 
and raise issues that are later explored in the Collecting and 
Interpreting Evidence section. The sequence of questions in 
the latter section prompts students to compare their experi-
mental observations with their predictions. As often happens, 
the experimental evidence supports some of their initial ideas 
but not others, prompting students to reconsider their initial 
ideas. Finally, the questions in the Summarizing Questions 
section, which address aspects of the key question for the 
activity, help students recognize what they have learned in 
the activity and how their fi nal ideas might have built on, and 
changed from, their initial ideas.
The second design principle is that learning is a complex 
process requiring scaffolding. 
During the learning process students move from the ideas they 
have prior to instruction toward ideas that are consistent with 
generally accepted principles and concepts with more explana-
tory power. This view of learning thus assumes that students’ 
knowledge develops gradually and that this process takes time. 
Such a learning process can be facilitated by providing a high 
degree of guidance and support (referred to as “scaffolding”) for 
students as they take their fi rst tentative steps in modifying their 
initial ideas. However, as they move toward mastering a certain 
concept or skill, the degree of related scaffolding provided can be 
gradually diminished.
In the PET curriculum guidance is provided within the 
structure of each activity. The Initial Ideas section helps stu-
dents make connections between what they are going to learn 
and what they already know. The Collecting and Interpreting 
Evidence section consists of a carefully designed sequence 
of questions that ask students to make predictions, carry out 
experimental observations, and draw conclusions. Guidance 
is especially provided to help students make sense of unex-
pected observations. Finally, in the Summarizing Questions 
section students are guided to synthesize what they had 
learned during the activity. 
The third design principle is that learning is facilitated