You have a wonderful attitude toward your parents and God definitely honors that! They may be more protective than most parents but that has been a blessing to you in many ways....their motivation is love for you and a desire to be godly parents.
It's normal and healthy to desire more freedom and as they see that you are responsible they will probably give you more freedom. You may have to talk to them honestly and respectfully and point out the logic of them giving you more opportunities to make your own choices. This is practice in 'living' and doing so within your parents protection and support is the way God intends for independence from your parents to grow.
I used to think the same about focusing on school and not working....but I've changed my mind about that
. There's a lot to learn in a new situation, especially about the value of money. A job can be an education all in itself; how to get along with others, how to function under authority (other than a parent), etc. Plus, this can give you a lot of self confidence. So if you can get a job working a few hours a week I think it would be good for you.
Praying for you and your parents...may the Spirit lead you into godly freedom while maintaining a good relationship with your parents.