The more you keep the attention of the children, the less you will have to correct them. Please remember this important rule: children only have the attention span of their age plus one. That means if you are working with 8 year olds, you only have their attention for 9 minutes, then you should go on to something else. This means you need to teach toward the attention span of the youngest ones in the class.
For example: If you usually have 20 minutes of music and you are ministering to 10 year olds, you should break up the music into two different times of 10 minutes each. You could possibly teach in between for 10 minutes and then go back into the music. It is not necessary or advantageous to make children sit there and listen to a teaching time for 30 minutes. You usually lose them after the first 10 minutes. If you are very creative (using props, songs, drama, puppets) then you may be able to extend the attention span time by a minute or two. But as a rule, 20 minutes is the most that you should do any segment of a children’s service.