Does anyone know what is used for graduation songs in Spanish?

You might want to try a Google search for Spanish graduation song. Typically, songs for graduations are those that are popular with young people at the time of their graduation. The songs themselves do not necessarily have to have anything to do with a graduation.

There is an old popular song in Spanish, LAS MAÑANITAS, that is used for various celebrations. The words could be changed to fit a graduation.

The songs melody is one that has been popular for many decades.