I am looking for a Scale that helps me to measure a kind of virtue predisposition in adolescence and young adulthood (high-schoolers and undergradute students) grounded in the aristotelian theory of virtues.
I read the links provided by Asad but I don't see any specific tie to Aristotelian virtues. May I suggest that you refer back to Aristotle's works and create your own scale - one which you can justify, point by point, by referring back to specific passages of his works. This creation, properly done, will enhance your gravitas on this subject. It may then be adopted by other researchers.
Virtues are universal in nature and these are the similar for centuries:
Links were provided to help initiate the idea of virtue ethics rubrics;
" There are many recognizable similarities between Aristotle’s concept of an arête of character and our modern concept of virtue. Both are the grounds for calling someone good or bad, for praising or blaming them for what they feel and do. Both are clearly dispositions of feeling and closely related to the sorts of choices people make. If we start to list traits we would call virtues, we see a large overlap with Aristotle’s list"(http://documents.routledge-interactive.s3.amazonaws.com/9781138793934/A22014/ethical_theories/Aristotle%20on%20virtue.pdf)
Curzer, H. J. (2012). Aristotle and the Virtues. Oxford University Press.
Sherman, N. (1989). The fabric of character: Aristotle's theory of virtue.
" In Book II, chap. vii, of the Nicomachean Ethics, Aristotle discusses a list of moral virtues or qualities essential to the good man. They are exactly twelve in number: (1) Courage, (2) Temperance, or Self-control, (3) Liberality, (4) Magnificence, (5) Highmindedness, (6) the mean concerning Ambition, (7) Gentleness, or Mansuetude, (8) Truthfulness, (9) Wittiness, or Jocularity, (10) Friendliness, or Courtesy, (11) Modesty, or Shame, and (12) Righteous Indignation"p.25( DeMoss, W. F. (1918). Spenser's Twelve Moral Virtues" According to Aristotle".(Continued). Modern Philology, 16(1), 23-38).
In order to answer your question, I need to put it in the big picture.
Aristotle himself left us a classification of his categories. You can find the logic-explanation in Aristotle’s Categories (which belong to the Organon). Virtue is part of categories, since virtue is a habit for Aristotle, and habits are a kind of the quality of rational beings. Aristotle distinguishes four kinds of qualities (that is one of the 10/8 categories or predicaments) that are grouped in couples:
1. Disposition/virtue
2. Impotency/potency
3. Passive quality/passion (or passiveness)
4. Shape/form
These different couples represent different “state” of the quality. So, disposition according to Aristotle (Cat. 8b/9a) are less stable and less durable/persistent/steady than virtue. Virtues in Greek is qualified as more stable and more persistent («μονιμώτερον καὶ πολυχρονιώτερον»).
The consequence of that is that, if you want to measure the first kind of quality, you should take into account the clear distinction between disposition and virtue.
The second consequence is that you should consider the difference in both between stability (so, that a behavior doesn’t fluctuate so much in itself) and persistency in time (a behavior is repeated constantly or most of times).
An example:
1. Disposition
a. Stability
b. Persistency in time
2. Virtue
a. Stability
b. Persistency in time
The more stability and persistency a student shows in six months, the closer to virtue. Peter doesn’t arrive on time for classes. He improves it, but doesn’t show consistence, and fails sometimes 3 times in the week, sometimes 2… This student has a disposition to punctuality, but not a virtue.
One should stablish some flexible criteria for both, disposition and virtue.
These are the simplest aristotelian basic-elements, in my opinion, of a possible predisposition for virtue scale.