Constructivism:

Definition: based on the premise that cognition (learning) is the result of "mental construction." In other words, students learn by fitting new information together with what they already know.

Also referred to as: student-centered,""child-centered," "learner-centered," "discovery-based," "self-directed,"

Supporting Articles:
An Interpretation Construction Approach to Constructivist Design
In Search of Brain-Based Education
from Piaget to Papert
Additional Articles on Constructivism

Constructivist Models
Constructivism in Practice: The Case for Meaning-Making in the Virtual World
The Learning Connection

Constructivist Models
PBL Buck Institute
The Project Approach ERIC

Instructivism:
Definition:Direct instruction by a teacher employing objectives and lesson plans related to an overall curriculum guide in order to teach specific content, customarily using the lecture method. Knowledge is in possession of the instructor.explicit teaching

Also referred to as: "direct instruction," "masterylearning," "explicit teaching," or "precision teaching,"

Supporting Articles
Education That Works: The Child is Always Right
Instruction The Tyranny of Dogma
Effective Schooling Practices:
A Research Synthesis 1995 Update
Direct Instruction-Research Proven

Direct Instruction Models
Direct Instruction: Robert Slavin's Model

For an excellent overview see:
Education Reform 1995-1996 - Chester E. Finn Jr. and Diane Ravitch A Report from the Educational Excellence Network ^{Edinformatics Select!}