I'm in your boat OP. Started nannying part time my last year of high school (mostly just because people kept asking me, not because I was particularly interested in it). In college I did my first year full time school part time nannying but by my second year was doing the opposite (full time nannying, part time school). During my last few years before graduation (bachelors in biology) I had internships at the DC zoo and (now defunct) aquarium.
I realized in those last few years of college that:
A) the careers I wanted in biology would require at least a masters degree if not a doctorate, which I could not afford because I had so much debt just from undergrad
B) the entry level careers I could've gotten in biology were either going to involve testing pharmaceuticals on animals or would involve extremely low wages and be salaried (no overtime) even though I'd likely be working 50-60 hours per week
C) nannying not only paid better than said entry level jobs but was honestly also a lot more fun than working with a bunch of underpaid whiny jerks (like those I worked with at the zoo and aquarium);
So, now I've been a full time nanny for 12 years. Sometimes I wish I could've gotten my dream job, but honestly the sort of work I wanted to do (working in the field with endangered animals) was just not something I could achieve without more money for schooling or better connections (GMU did not offer many opportunities at all for biology students in terms of career assistance or even research opportunities with professors). I did job search for opportunities in the field within my grasp (such as working as a lab tech or for the local fishery and wildlife organizations), but every time the pay was lower than I made as a nanny (and the fishery and wildlife and forest jobs are always only seasonal, so I'm not sure how they expect their employees to survive in the winter??).
Overall I really enjoy the time spent with my charges as a nanny. I love playing board games, doing arts and crafts, playing at the park, and of course smiles and hugs, which I know I get a lot more of here than I ever would've stuck in a biology lab or at a desk.