KS3:Try the Smartie model. It is not perfect, but at least helps your students understand some basic principles about currents. You act as the battery. You have a supply of Smarties, that you can give to your electrons (students). A current is made up of moving electrons, and in this model your students move around the circuit. When your students move past the battery give them two Smarties each. Start off with a series circuit. Mark out a circle and place two stools at opposite sides. Position the battery on the circle. As your students move around the circle they need to climb over each stool. This requires energy - so get them to eat a Smartie (voltage) when they climb over each stool. The energy is divided between the two resistors. Now create a parallel circuit. Make two separate pathways (like the rungs on a ladder), each containing one stool. Position the battery as before, and give your students two Smarties each. They choose a pathway to go down. Each pathway has only one stool and they must use up all their energy climbing over this stool by eating both Smarties.
They get the whole amount of energy, but the current is split.
Don't be tempted to repeat the TTA advert for teaching with everyone crowded round a Van de Graaff generator. The shocks are huge so follow safety guidelines.