Oi gave a very thorough explanation, now I will give my twopence worth.

The more used terms are freshman, or sophomore, depending of how long you are in

the academy (at the university, I mean).

 To say "calouro" in educational circles they might use some words, for example:

 freshman, beggining student, begginer, novice, tenderfoot (a little jocose here).  

You also can find, here and there, used in a general way:  "fresher" (UK) or  "novice" (novato).

Sources - dictionaries :

-Webster´s Dic. Univ. participation Houaiss/Ismael Cardim

-Collins Prático

 -Webster´s Port.-Eng. Dict. by James Taylor -Revised Edition.

-Larousse Avançado  Ing.-Port.   Port.-Ing.

-PP (that is, I myself).

Hope it helps.