I would definitely argue with that health teacher!! 1,500 calories is too low for an active young male.
I'd go with your original comment...Eat plenty, but eliminate "empty calories," those things like soft drinks, chips, candy, etc. that contain lots of calories but hardly any vitamins or minerals. Drink lots of water, eat as many fruits and veggies as you can, eat wheat bread instead of white whenever possible, and things like that.
The problem may be the 6 miles a day thing. I don't know what kind of bike you have or how hilly your route is, but try to get in at least 30 minutes of riding at a pretty good intensity. Depending on your bike, the hills, the wind, etc., you may be getting that much as it is, but if you're riding a road bike on pretty flat land (Florida), then 6 miles probably doesn't take 30 minutes.
Don't try to eat less (you should probably eat at least 2000 cal a day), but eat smarter instead. I know it's a lot easier said than done, especially if you're young and a lot of times don't control what your parents buy at the store.
Most importantly, be patient. How long have you been trying to lose weight? Unfortunately, losing weight is a pretty slow process. Also, you may find it more useful to gague your progress by how you look and feel, not only by what the scale tells you.