There is an order-effect confound. Half the subjects should get the colas in reverse order. Amount of practice is confounded with distribution of trials. Flunking out and self-esteem are correlated but that does not mean that one causes the other.
Treatment is correlated with exposure to the situation and passage of time.
Need a control condition that is exposed to everything except real biofeedback. Need to include two more groups tested on an easy task to test the hypothesis. Need to assess whether the level of fear was different between the groups. Both groups may have been very afraid. A control group that did not get the threat of shock would be useful.