Effective assessment is vital in educational activities. We propose IWAS (intelligent Web-based assessment system), an intelligent, generalized and real-time system to assess both learning and teaching. IWAS provides a foundation for more efficiency in instructional activities and, ultimately, students' performances. Our contributions are summarized as: (1) Given the causes (student knowledge levels and learning styles), BN (Bayesian Networks) technique is utilized to automatically reason on the probabilities of the presence of the effects (learning outcomes); (2) The absence of teaching practice assessments is addressed via the feedbacks from three different levels, aiming to correlate the teaching assessment with the learning assessments for the improved effectiveness in instructional activities; (3) Under a client/server architecture, IWAS is decomposed into a set of independent modules; through the standard inter-module interfaces, the flexibility of easy maintenance makes IWAS a generalized system adaptable to different domains; and (4) Web technologies are integrated to deliver the formative feedbacks to users in a timely manner. (Contains 1 table and 2 figures.)