The scariest thing every teacher has to contend with is that no matter how sincere we are, no matter how well read, and even with the Holy Spirit Himself teaching them, they are not infallible. Your pastor is not infallible. Your favourite preacher is not infallible. I am certainly not infallible. My brethren, according to none other than the brother of Jesus, guided by the Holy Spirit, even the Apostles stumbled in many ways.
We actually see an example of this in Galatians 2. From verse 11 onward, we see that Paul, who by his own words wasn't even worthy to be an Apostle (1 Corinthians 15:9), rebuked Peter for the sin of hypocrisy. Peter's sin, which actually spread to Barnabas as well (v13), was compelling gentiles to live as Jews, even though in Christ, not even the Jews themselves are under the law.
For teachers, this should be terrifying. If someone makes their own mistakes, that's one thing. But because people look up to teachers, sometimes not even stopping to question them, a teacher's error spreads. Therefore, James tells us that teachers will face a stricter judgement.
For everyone else, this should be a warning. You may not face as strict a judgement as your teachers, but because they can still stumble, they can cause you to do likewise. Therefore, you should test even your teachers. It is there responsibility to teach you the truth without error, it is your responsibility to receive the truth without receiving the errors. Remember this: None are infallible but God.
Post publication note: Normally, when these articles go live, I'll proofread them one more time and correct any errors. This time, I made a rather embarrassing mistake, but rather than edit it out, I have decided to leave it there, and highlight it, further illustrating the point that people you learn from can make mistakes.