Nope, no one sends letters home. It's your education, not your parents'.
If your cumulative average at the end of the year is BELOW a 3, you are kicked out and have to wait one full year to apply again if that's what you want.
If it is a 3.1 - 3.4, you're placed on academic probatation for one reviewing period (i.e. one term) and have to get your average up in order to continue at the university. It's basically like a warning; They send you a letter at the end of the term if your average is in area and they tell you to step it up or you're out. Note that you can only be on academic probation ONCE during your university career, so try to try kick ass on your finals.
If your average is a 3.5+, you are in decent academic standing and don't have to worry about getting kicked out, at least for now.
Keep in mind, though, that most programs require a cumulative average of 6, so work hard next term.