This paper describes a general model for the design of stand-alone intelligent assessing systems. According to this model, a prototype system supporting the assessment of students of age 8-12 who show a low performance in arithmetic word problem solving has been implemented. The main purpose of the underlying research is to study the difficulties the expert part of the computer system faces trying to adapt the teaching goals to the knowledge, strengths, and learning preferences of the individual student, taking under consideration his/her current motivational state.