If you plan on being an ATC at KSFO, you better know what you are doing. I fly in and out of KSFO frequently. I don't mind if you make a mistake or two, but if you leave me at 6000 feet above the threshold 3 miles from touchdown, you failed. You are fired. BTW, I trained air traffic controllers at Los Angeles ARTCC from 1978 to 1981. My supervisor called me a "long haired arrogant asshole with an overbearing god complex". I have changed. I got my hair cut. He also said he would have fired me a long time ago if I wasn't so f**king good at what I did.
Edit: Things are much better at KSFO. Don't know if it is the same person, but much more polite and organized. Just FYI.