what is the minimum amount of weight that a 6 foot tall, 160 pound 14 year old boy should be able to bench press?
What do you mean by minimum? The minimum to avoid being made fun of? The minimum to be considered strong? I would say a beginning goal of a healthy young man would be to do their body weight, so 160 pounds. When I first started bench pressing at around 15 years old, I think I weighed about 150 and ended up doing around 180-185 at the end of the school year. I was naturally strong though, so that may have been above average. Keep working hard and challenging your muscles, and you'll be worrying about maximums instead of minimums!
There is no minimum weight any one should be doing. It all depends on how you were built. Try maxing out, see what you can do. And do repetitions of a certain percentage of that weight when you work out. Try 45% of your max. Then when that starts becoming easier go with 50% of your max.