"Colación" is the act of granting degrees. UTN places us in Argentina, I believe. The date in the extract you have quoted shows that it refers to an event. Clearly it means the student with the highest average out of the cohort graduating on that date, and it might be expressed differently in English (for example, "highest average grade/GPA in the graduating class of 2012", in American English), but "colación" is specifically the formal granting of degrees, and I think you should translate it as it stands: "highest average grade at the graduation ceremony (held) on 07/12/2009".

"colación
1. f. Acto de colar o conferir canónicamente un beneficio eclesiástico, o de conferir un grado de universidad."
https://dle.rae.es/?id=9j9t8Cr

Although this is not marked as a regional usage, "colación" is not generally used in this sense in Spain, in my experience.

"CEREMONIAS DE COLACIÓN DE INGENIERÍAS/LICENCIATURAS. •16.00 hs:"
https://www.frba.utn.edu.ar/graduados/cronograma-ceremonia-c...

"Graduation ceremony" is a generic term in general use both in the United States and in the UK, though some universities use other terms. It's called the "degree ceremony" at a number of British universities and Harvard calls it "commencement".