In human terms the priest Eli was. However Eli could not even teach his own boys right. God would have been the most effective teacher Samuel had. Evidently Samuel learned to listen well and to follow God and not the bad example of man, at least in terms of his own leadership of Israel. As far as Samuel's own children went, it seems he didn't do much better than Eli - this was one contributing factor to the Israelites wanting a king.
In the Bible, Eli is Samuel's teacher. Eli was a High Priest of Shiloh. Samuel was a leader in ancient Israel, and the name Samuel means 'name of God.'