Being a pre-nursing student about to start nursing school in spring 2020, I would suggest to not try to take more than you can handle and risk getting bad grades. I am a full-time student and take 13 credit hours each semester and during summer I take 6 credit hours and that is a lot for me. Keep in mind I do not work, school is my full-time job. science courses require a lot of attention, and I also don't recommend taking more than one science course at the same time. It is totally possible to do it though, I've heard about people doing it but personally, it's hard for me.