Well, I believe it depends on the conservatory. I was accepted last month (in composition), and the classes have just started. It's a four-years long university-level course in a local conservatoire here, north of Brazil, in a city called Belém.
I recommend you to go there and search for the past exams requirements. They usually inform in some kind of publication all the contents you should study in order to have a good exam. I my case (composition), we had a theoretical test, which included rhythm, harmonic analysis (rudiments), voice leading in 4-part harmony, western classical music history (mainly the eras, some composers and characteristics), enharmonic spelling, intervals, chord progressions and rhythmic-melodic dictation, among other similar things. The following day we had a practical test, in which I had to sight-read a solfege (and it has terrible), play a piece on my instrument (any piece; I played a Chopin's mazurka in C#m), present two compositions of mine, with at least one of them being played live (I played a nocturne of mine on the piano), whlie the other could be played on a CD player (I brought a trio for piano, flute and clarinet, which is BTW posted here).
I got accepted! 1st place!