"TEACHER" is me. zxc555" in comment #6 reminds me of a story in the Tipitaka:

The Buddha was on his way back to see the five teachers he had received instructions before he left them to try out various methods of learning on his own. He met a brahman who praised his look and aura of a learned person. The brahman asked "who is your teacher?". The buddha said "I have learned by myself. I have no teacher." The brahman resolved to walking away. The Buddha never again said that he had no teacher. Even the Buddha did learn more after his Enlightenment.

Perhaps many more stories in the Vinaya would show how the Buddha learned more from his disciples and others.

There is no doubt that the Buddha was (and still is) a Teacher, even when death was imminent. His last teaching was that we should live with 'not carelessness'. Then, He disrobed unattaching his Body to the world.