I'm scoring very high on all sections of the ACT except for the science section. I consistently get almost half of the questions wrong. What can I do to improve my performance?
The best way to improve on the ACT Science section is to pay close attention to diagrams and eliminate irrelevant information in the questions and passages. ACT Science is tricky because it looks complicated, but it's not all that hard if you avoid distractions. Underline the important parts of the questions, and stay focused on them. Don't worry too much about the wordy introductions. The diagrams are where you'll find almost all the information you need to answer each question.
I'd also recommend that you do the Conflicting Viewpoints passage last. It tends to take the longest because it involves the most reading. Check out this article for more great ACT Science tips: http://blog.prepscholar.com/top-6-act-science-tips-you-must-use.