A tween's school day is dedicated to her acquiring necessary knowledge, or learning what she's supposed to learn. But after school, there's a wide window of opportunity to try out activities or subjects that aren't part of the school curriculum.
This is why so many tweens take classes like yoga and Zumba, or dance at a private dance studio or gym. Specialized fitness classes typically aren't offered through schools, especially for those in the tween age range. Classes are a great way to beef up coordination and skills before entering junior high or high school. Additional years of practice can give kids an extra edge before trying out for sports or clubs at higher levels of ability.
There are plenty of classes beyond athletics. If your tween's 30-minute art class at school isn't enough, enroll her in a drawing, painting or sculpting class after school. Maybe he's shown an interest in learning a foreign language; why not find a private tutor to teach him Spanish, French or Italian? And if your tween is the unofficial sous chef at home, sign her up for cooking classes so she can perfect her craft.