You aren't alone; almost everyone who's ever taught this age group probably has felt the same way at one time or another! But I hope you won't give up -- not until God leads you to do so.
I often think of Jesus' parable of the seed and the sower (you can find it in Luke 8:4-15). In this passage, Jesus told about a farmer who sowed seed in his field. Some of it failed to grow; it was choked by weeds, or fell on hard soil, or landed among the rocks where it couldn't put down roots. But some, Jesus said, fell on good soil -- and eventually produced a bountiful crop.
This, Jesus said, is what happens when we teach or preach God's Word. Not everyone welcomes it, but some will, and God will use the "seed" of His Word to produce lasting faith. It may take time, but God has promised to bless His Word.
Pray regularly for the members of your class. Ask God also to help you be the best teacher you can possibly be -- well-prepared, interesting, kind, and so forth. (You might ask another teacher you trust to sit in and suggest ways you can be a better communicator.) Above all, point your students to Jesus and His love, and urge them to open their hearts to Him. And trust God's promise that His Word "will not return to me empty, but will accomplish what I desire and achieve the purpose for which I sent it" (Isaiah 55:11).