Harry may not know coffee is available. Harry may have come to believe that coffee is dangerous to his health whereas tea is not. We can generalize from this to recognize that certain conditions enable the expression of a value. They are knowledge, ability, opportunity, and priority. If one of these conditions is lacking, a value may not be expressed in behavior.
Priority is a tough one.
We would have to know many of the other values of each subject and their relative ranking in order to construct a test situation so that competing values did not interfere. This is not to say that the schools don't teach kids values. Consider, for example, a situation I witnessed in a high school I once taught in. Feeling that school spirit was low, the principal has seniors and juniors brought to the auditorium for a pep rally the day before a major football game. But as trumpets blare, drums boom and female cheerleaders somersault, interest is aroused.