1. A method using a video based teaching aid, the method comprising: (I) performing an off-line training process, which includes: (i) acquiring a surveillance video sequence using at least one video camera operatively connected to a computer; (ii) for a given video image frame in the video sequence, detecting one or more face images present in the video image frame; (iii) for at least one detected face image, automatically performing facial region operations; (iv) processing each detected face image to increase robustness to lighting and scale variation; (v) assigning each detected face image to an expression category or label; (vi) calculating representative features for the face image; (vii) determining a correspondence between the representative features and the expression category or label; (viii) repeating the expression category or labeling steps of (ii)-(vii) until all faces of interest have been processed resulting in a labeled feature set; and (ix) training a classifier using the labeled feature set; (II) performing online operations which include: (i) recording video images of at least some of a plurality of people in a classroom setting by use of a video camera arrangement; (ii) identifying expressions of the people in the video images by use of an expression recognition module configured to receive the video images from the video camera arrangement, the identifying including automatically localizing, for at least one detected frame including a human face image, a periocular region associated with the human face image and segmenting a facial region of the frame including the human face image based on geometric ratios about the periocular region; (iii) correlating the identified expressions of the people in the video images with at least one of an event or an outcome of an event, including but not limited to taking a test, occurring in the classroom setting by use of a correlation module; (iv) automatically classifying the identified expression using the identified expressions and the trained classifier generated in the off-line training stage; (v) outputting results of the correlating by an output device, wherein the recording of the video images includes obtaining a time-series or progression of facial expression changes during a teaching process, including a negative facial expression progression of people in the classroom which intensifies as time progresses, wherein this is interpreted by the output as a negative indication regarding the test, and wherein the recording of the video images includes, identifying a distribution of confused expressions of people taking the test clustered around a particular group of questions, wherein the output identifies this as an indication the particular group of questions were confusingly drafted.