Pay attention in class. Turn your phone off, and don't allow your classmates to disrupt your learning.
Take notes. Taking a picture of the board always SEEMS like a good idea, but research tells us that it is better for your brain and information retention if you write things down.
Ask questions. You are in charge of your learning. If you don't understand something, or need clarification, ask! :) Advocating for yourself is a skill that will help you immeasurably in your future.
Write down assignments and their due dates. Schedule time in your day to complete work. Even if the assignment doesn't count for a grade, it is preparing you for the summative task. Homework = practice, and practice makes permanent.
Get tutoring if you need it. There are teachers and students available to help you in the resource center during your free periods. There is also tutoring offered afterschool.
Study. For a minimum of 20 mins before bed, study. Reread your class notes, do flashcards/Quizlet. Watch a YouTube video about the topic you're studying. Tutor someone else.
Retakes- many classes offer retakes for assignments/tests. Take advantage of the opportunity to show that you have learned the classroom material.
Get involved! Students that are involved in clubs and sports tend to perform better academically. Not sure where to start? Ask a teacher.
Take care of yourself. Get plenty of rest, fluids, and food. Place a high value on your physical and mental health. Try yoga, or meditation. Balance your school, social, and work life.