Your student will care about practicing as much as you care about their practicing. The reality is that your student is 11-14 years old, and they don't always like doing what's good for them. We are guessing that your student might not like eating their vegetables, or doing their math homework, or reading the books they need to read for school. Practicing often falls into that same category. If you want your student to do well in band, you are going to have to make sure they are practicing at home, just like if you want your student to be healthy, you have to make sure they exercise and eat right. The better your student sounds, the better they will feel about their instrument and being in band. They may not want to practice (hardly anyone does), but they need to. You may not want to fight them to practice, but you may need to, and if you do, it doesn't mean they shouldn't be in band. If your child puts up a fight about practicing sometimes, it just means that your child is normal. Trust us! Practicing is work, and no one likes to do work.
Talk to your student about practicing often, and ask what they are working on. Ask them to teach you something. They will like knowing something you don't know, and you will like understanding some of what they are doing. Your student should practice 20-30 minutes a day, five days a week.