... join the Royal Navy at 17, female, would I be able to stay in school to do A-levels? And also go to university?

Also, I did a psychometric test a few days ago and passed, but my open jobs were warfare specialist, which I find quite interesting, (and a few others). However, although the career I want to do is marine engineer officer, I couldn't do this because I don't have a degree. (There was a mix-up when an officer in my school told me I could apply for this, when clearly I couldn't, which I was confused about). At the unit, I was told to go away and have a good think about the warfare specialist job though.

So, do you think I should wait before joining the Navy until I finish my a-levels and then have a degree in engineering at uni? Or, go ahead and do warfare specialist at 17 years of age, (only if it's certain that I will still be in school doing A-levels and then going to uni)???

Finally, if I were to do warfare specialist now, is it possible to change my job as a marine engineer officer once I complete my a-levels and get a degree?? Or does it not work like that??

Thanks