Abstract: A system and method are provided of analyzing a response expression in a freeform format as entered by a student in response to testing and practice questions presented by a computer system. The method can include parsing the response expression into tokens stored in a response expression tree. The system can determine whether the response expression tree is legal based on a defined grammar structure. Another operation is comparing a numerical evaluation of the response expression to a numerical evaluation of a reference expression. The similarity between the response expression and the reference expression can then be determined by comparing the response expression tree and a reference expression tree. Feedback can be supplied to the student regarding the overall correctness of the response expression as compared to the reference expression, based on correctness of each response expression element and the types of errors among response elements.