Saab 340 flight crew experienced two missed approaches due to less than adequate vector and altitude assignments; the reporter indicating training was being conducted.

Narrative

During descent into the terminal area; it became clear to the First Officer and I that our descent and our vectors would not result in a stabilized ILS approach. While on this frequency; I could hear a student Air Traffic Controller working several other aircraft in the area and I could hear an Air Traffic Controller Supervisor step in several times with corrections and 'disregard' messages to aircraft. After being cleared for the approach; too high and too close to the airport; and sent over to the Tower frequency; the First Officer and I initiated a missed approach procedure before descending much farther. Once back on the Approach frequency; we were vectored back around the RADAR pattern by the same student Controller. Upon the final dogleg vector; the First Officer and I discussed that this vector also did not look good; but there was a chance we could fly a stable approach. After the glide slope came alive and descended through our altitude with the localizer needle still pegged at the wall; the First Officer directed another missed approach procedure. Upon declaring the second missed approach with Approach Control; the Supervisor Controller apologized and we were vectored around one more time. I asked Approach Control for an extended downwind leg to allow for a stabilized final approach. After these extended vectors; a stabilized approach was flown to an uneventful landing. I was perturbed by this event; because I knew that a Controller was being trained during our approach. However I expected to hear the Supervisor that I had heard step in with other aircraft; step in to ensure that our flight was able to comply with ATC instructions and still fly a safe and stabilized approach. Once this did not happen the first time; I expected to hear the Supervisor's voice during the second approach. When this did not happen and a second missed approach resulted out of those poor vectors for the second time; it was clear that the Supervisor's decision was not in the best interest of the safety of our flight. This main decision put Controller training as a priority over safety. As a result; the task load on crew members increased; our fuel diminished; and our safety margin eroded. Had the third set of clearances not resulted in a stabilized approach; the First Officer and I would have diverted to our alternate.