Don’t make them attend church/youth group. After all, church is only for those who feel like going. If they are too tired or just don’t like it that much, assure them those are valid reasons to opt out of fellowship with other believers.
Make sure they are entertained, not equipped. Priorities, after all: if all your youth group is doing is teaching them to follow Jesus, without sufficient fun saturating the event, it is time for a change.
Speaking of priorities and attendance, let them skip church/youth group any time you have a schedule conflict. No one would argue that homework and extracurricular activities are more important than gathering with the saints. This will also prepare them for the future, when careers and hobbies will climb above church on the priority list.
Don’t correct them if they complain about church/youth group. Complaining is only a minor sin, remember. (I can only think of one generation that God wiped out entirely because of it.) They don’t need loving rebuke; they need laughter and participation in their immaturity, else their self-esteem might suffer.
In fact, when they complain, bring it to the youth pastor. That way they’ll learn the real problem is the leaders, and—more importantly—they’ll learn that they know more than their pastors about ministry anyway. (That bit about making it a joy for your leaders to lead doesn’t apply to youth pastors.)
Ground them from youth group when they misbehave or get low grades. Church is like a cell phone—a distraction to be removed when behaviors get careless—not an indispensable means of grace. And if they struggle with obedience to the commands of God, the last thing they need is a community of believers facing the same issues and striving to grow in grace together!
When all else fails, change churches regularly. Remember, it’s not about unfailing commitment to a local congregation because of your membership in the body of Christ; it’s about making sure your needs are met. The only way to make sure that happens is to leave every time you’re unhappy. I would recommend at least one switch, and preferably two, during their teen years.