There is something contagious out there in your youth groups, hopefully, which needs to be identified and harnessed. This is the infectious power of your youth's love for the Lord Jesus Christ. Who do they infect outside of their youth group? I think the biggest group affected by youth ministry is the parents. Just as it is there primary job to lead their student in the way of the Lord, they are one of the most highly affected groups when it comes to youth ministry. Every day with a youth brings a new experience to the table; a new trial or test that can deepen or weaken a teenager's hold on their security blanket of religion. Parents learn from their parenting mistakes, they grow; they develop new strategies to take new ventures. Who are the primary people who affect parents? Their youth.
The Youth Pastor is affected by the youth ministry.
If their group is growing and becoming more "like Christ" than the Youth Pastor will be encouraged and will be a nice guy to talk to. If their group is a bunch of bums who have no direction and youth group is nothing more than a hangout, it directly correlates to how the Youth Pastor is leading and hard the Youth Pastor is going to have to work to turn it around. Too often youth ministry also becomes about numbers and too many times a youth pastor is let go because their church is playing the "numbers game" (Fields, First Two Years of Youth Ministry) The Church Staff and membership is affected by youth ministry. Bryan Gott was quoted saying "Youth Ministry is still the "Evil-stepchild" of the church." I think this is a clever way of putting it. Just like the model of the one-eared Mickey Mouse, (Dean & Foster, Godbearing Life 29-31) it is too often that we find churches that want nothing to do with their youth and will pay them off in assurance that they will be out their hair. The Church Staff and membership are affected in both ways. They will be affected if your group is doing well or your group is doing poorly. If your youth group is not producing what your church would call "productive" results than your funding will likely be affected. If your group is doing quite well they will be affected because there will be more "youth" in their life. A successful youth ministry would be incorporating youth ministry into every aspect of church life. When I asked my secretary at church she replied that she would love to be more useful to the youth ministry if only she was asked to do us. Involving the church with your youth is just as important is involving your youth with your church.
Schools are affected by effective youth ministry. Your youth spend more time at school then any other place from the age of 7 all the way through the age of 18. This is a pivotal place of influence. Youth groups that produce healthy "core" youth will send those youth to contaminate their schools with the love of Christ that is within them. You might find it ironic that I used the word "contaminate" and "love of Christ" in the same sentence. I use it in the sense that I picture their every essence to be spewing Christ; it will be littering the courtyards with Jesus. People walking with you to class, people eating lunch with you will be getting Jesus all over them.
Youth Ministry affects the surrounding neighborhood of the church. How often do you hear of complaints from the surrounding neighborhood because the outside music was way too loud or that the youth trashed the neighborhood when they went on that scavenger hunt the other week. If you want to know how your youth is impacting the communities just ask your next door neighbors. If they actually know what is going on with your church and have a good attitude about your program then you will know that your youth is impacting your community for the positive. If they have no idea what your church is about and tell you a horror story about how at the last scavenger hunt someone drove across their lawn and didn't even apologize you may need to rethink how you are impacting your community.