Ministry is spelled w-o-r-k. Ministry is doing God’s business. We can work in or work on the business. Both are important, but there is a big difference between the two. We need to be able to realize the difference to be sure we are doing both. In every ministry, including children’s ministry there are at least 2 kinds of jobs: $10/hour jobs and $100/hour jobs.  The $10/hour jobs include scheduling, copying, keeping up with supplies, and maintenance type work.  The $10/hour jobs are working in the ministry. These are the hands on, nuts and bolts parts of ministry. The $100/hour work includes: establishing long range goals and making plans to reach them, creating a management succession plan, establishing an emergency plan (what to do when things go wrong). The $100/hour jobs are working on the ministry, they are the vision, expanding, and leadership part of ministry. With is this approach lets look at a few connected thoughts.
Each person needs to do $10/hour jobs and $100/hour jobs. Your position may dictate the amount of time you appropriate to each job. A person in charge should spend most of their time working on the ministry but also working in the ministry will help them to lead those that mostly work in the ministry. An assistant would spend most of their time working in the ministry, but they need to do $100/hour jobs by working on the ministry as well.  This it will help them to mature and be grateful of to those leading. Caution: leading and assisting are not classes of people but types of positions. The Holy Ghost is a helper but is not lesser than the Father or Jesus.   
There are so many $10/hour jobs that need to be done in every ministry, that it isn't surprising that most of our time is spent working in the ministry. Working in the ministry jobs are usually very pressing but are not always needful. Working on the ministry is always needful but not pressing. Sometimes we neglect the working on the ministry.
The classroom should be time for working on the ministry. In the class room, as a teacher, make this job a $100/hour job by reaching into the lives of the children and creating positive change that can only accomplished by fellowship with the Father through  the Word and by the Holy Ghost. Make teaching a $100/ hour job by instilling a passion and vision for the children in other workers/teachers. Never allow your class to be $10/hour work by having a just get it done attitude.
Just as there are two kinds of work in ministry, there are two kinds of time.  We have time when we are worth $100/hour and time when we are only worth $10/hour.  For most of us the $100 hour time comes first thing in the morning.  What do most of us do in our $100/hour time?  We do our $10/hour work.  If we ever get to the $100/hour jobs, it is usually after we are worn out from a day of working in the ministry and we are only worth $10/hour, if that.
Evaluate yourself. Am I doing both working in and on the ministry? Am I dong $100/hour work at $100/hour time? Is my class $100/hour work?