@Blossom_Utonium
Howdy! Life-long Christian here! I though I'd give you some things to look into to make your character a little more realistic.
-In my personal experience, a lot of Christian kids listen to worship music, but it's not the only thing they listen to.
-Research the difference in denominations. Christianity differs greatly depending on what church you went to in what part of the country, etc.
-Most Christians tithe, which is giving 10% of their income to God (by dropping it in the donation bucket at church).
-Many churches vary wildly on their beliefs on LGBTQIA+ people. The church I grew up in does not agree with that lifestyle, but loves and respects people of all genders.
-Lots of Christian teenagers do church on Sundays, but will also attend Youth Group during the week, usually at night. Mine was on Wednesday night. What happens can vary from group to group, but ours was a sermon unrelated to the Sunday one, and then group discussions.
-A lot of parents will encourage their kids to volunteer in different areas of their church, such as childcare, the worship team, and so forth.
-The more strict their upbringing, the wilder most Christian kids get. Seriously, it's a thing. They do absolutely crazy stuff.
-Church merch! If your teen attends lots of youth conferences or special church events, they may own a lot of merchandise with bible verses on it. I know I have about 5 of those shirts in my closet right now.
-In my experience, most Christian teens aren't completely naïve. They know about things that you wouldn't expect them to know.
-Some Youth Groups do a sleepaway camp in the summer and another during the winter.
-Churches have multiple services in one Sunday. My church on any given Sunday had 1st & 2nd service (same message, different times), traditions service (hymns instead of modern worship), as well as services in Spanish.
-Whether or not Catholics & Mormons are fall under the umbrella of Judeo-Christians is an extremely hot topic, and can vary from church to church.
-Many Christian teens grew up watching VeggieTales. Look into it.
-Not every church is stuffy. Many modern churches don't really care what you wear to service, as long as you're clothed. In my experience, I always dressed up because it was my one chance during the week to do so.
-Depending on the size of the church, and how long you've been attending, you'll get to know a lot of the pastors and staff. Many are very accessible and will meet with congregants outside of church just to visit.
-Some churches offer counseling services.
-Many churches have pastors for each area of the church, such as worship, kids ministry, youth ministry, and outreach stuff, in addition to a "lead" or "head" pastor who leads the church.
-For a lot of teens, going on a missions trip to someplace far away with their youth group is the thing to do, if they can afford it. Think places like Mexico and Africa.
-Christian kids that spent their lives in church will be able to rattle off a plot summary of most Bible stories, such as Noah & the flood, Adam & Eve, Jesus' birth and eventual death/resurrection, etc. These stories are used a lot in sermons.
-Do some research into apologetics, which is the study of proving God's existence using logic and science. Some hard-core Christian parents will have their teens read books about this.
-If you settle on a denomination, look into their organizational structure. Most have national leadership, then district leadership, followed by individual church leadership.
-My church had a cafe and coffee shop inside.
-A lot of Christian teens have the issue of having "church friends" and "not church friends." I know in my personal experience, whenever I would have a party, I would often pick one or the other, instead of trying to get them to combine.
-There are many different versions of the Bible. Research it.
-Female pastors are another hot topic. Some say yes, some say no, it depends on the church.
-Most churches experience an influx of newcomers before and after Easter, Christmas, and New Years.
-Many youth groups push their students to invite lots of friends.
Basically, if you takeaway nothing else: every church does things differently.