The Argentine Government’s official international students webpage has information in English on immigration requirements for overseas students: http://estudiarenargentina.siu.edu.ar/.
Most nationalities can enter Argentina for up to 90 days without a visa. To find out whether you need a visa to enter Argentina, go to the government’s Immigrations page: http://www.migraciones.gov.ar/accesible/?visas. The Argentine customs website also has a list of Argentine embassies and consulates abroad: http://www.aduanaargentina.com/listado.php?seccion=22.
Citizens from the Mercosur region need only their national ID to enter the country.
Citizens from the United States, Australia and Canada need to pay a reciprocity fee (which is valid for several years) in order to enter the country. Click on this page to find out how: https://virtual.provincianet.com.ar/ArgentineTaxes/ or download the online payment instructions in English below.
Please make sure you check with your academic institution to see whether you require a student visa. Student visas can be obtained after you enter Argentina as a tourist, provided that you have the right documentation. For students staying more than 90 days, a student visa is usually a prerequisite.
Note that student visas are usually only issued for a period of six months, and will need to be renewed if you are planning to stay longer.