Subject choices

Hello! As a fellow highers student, I would strongly recommend you doing the subjects you are good at and enjoy - because highers is, if not the most, stressful year in high school and crashing a subject makes life harder than it already is (because you need to first review national 5 content before moving on to highers, which is double the work). If you really wish to take higher biology, you can crash it in s6, where you have less subjects and more time to revise each of them.
Hope this helps!!