Your school should publish a chart that details the calculation of a grade point average and for converting its grades into other common grading systems.
Graduate committees (or often at some point earleir in the admissions process before the departmental admissions committee even sees the application) will usually convert the transcripts from all applicants into a common scale. This common scale can then be used to determine whether the candidates meet minimum requirements for admission and then rank candidates relative to each other.
In that sense an A- is generally high enough to meet minimum admission standards, and seen as below an A, but above a B+. Further details will depend on the specific school.