"For ye see your calling, brethren, how that not many wise men after the flesh, not many mighty, not many noble, are called: but God hath chosen the foolish things of the world to confound the wise; and God hath chosen the weak things of the world to confound the things which are mighty"
God doesn't want to use people who consider themselves good teachers, good leaders, good anything in the secular world. He will use foolish things to confound the wise. God wants to use meek, moldable people. He will equip those He has called with whatever skills are needed to perform a job.
If God calls you to be a teacher you may say, "I'm no good as a teacher." He doesn't want teaching skills; He wants your heart, or your love, or your sense of humor, or whatever gifts He has given you. He will equip you, or has already equipped you, for the job.
In God's world we are not teachers, we are "Life Changers." Two good examples of people called by God that felt inadequate for the tasks God gave them were Moses and Paul. They did have the choice to refuse the calling God laid upon their hearts, you know. Once you have knowledge about Jesus you have the responsibility to, "Go, ye into all the world, and preach the gospel to every creature." (Mark 16:15)
Your portion may be in your own church, or in your own neighborhood, or in your own home. When God "doinks" you on the head with a commission, don't ignore it or shrug it off. Go with it, let God equip you, and you will be blessed!!