I recommend studying hard. Life may be good now with your parents' support, however, someday you will have to provide for yourself and your own family when you have one.
I did the hard yards at school and university and ended up graduating the top of my year and received the gold medal. This allowed me to pick whatever job I wanted, so in short it gave me more choice. Now I have a fantastic life and am comfortable.
They say that grades don't matter in the long run, and this is true. They do matter though when you are getting selected for Colledge/Uni (whatever you call it over there), and they matter when you are getting your first job. After that you rely on your professional reputation and track record - but getting that first job is crucial to your future.
Make sure it is a good future. Make sure you give yourself the lattitude to have as much choice as possible. There will be nothing worse than having a worse life in the future and not being able to achieve all that you want to acheive because you cut yourself short.
That doesn't mean that you shouldn't enjoy the car - indeed enjoy it, as you should enjoy each and every day, live in the now for sure, but remember that your now is creating your tomorrow... you can rely on luck, but hard work is more certain to pay dividends.
As for the public/private debate, I went to a public school and I still did well. If I had children I would send them to a private school though because I would want them to have every opportunity possible to have a successful life. Sometimes the value of a school isn't just the academic curriculum, but also the attutudes and values imbued and the social networks that are set up. Private schools seem to be much better in this regard - in Australia at least.
'05 E90 325i 6sp Man SG 118,032km on the odo (retired) | '06 E90 325i Step SG 121,021km on the odo (retired)
'08 E90 325i LCI Step SG 130,024km on the odo (retired)
'13 D30 328i M-Sport Step | EB II | Black/Aluminimum | Pro Nav | Xenon HBA | Lane Change Assist 24,760km on the odo