To achieve a successful turnaround in your high school English grades, focus on the following strategies:

1. **Consistent Reading**: Immerse yourself in various types of literature to improve comprehension and vocabulary.

3. **Practice Writing**: Write essays, stories, or diary entries regularly to hone your skills in grammar, sentence structure, and expression.

4. **Grammar Review**: Review common grammatical rules and practice with exercises to avoid mistakes.

6. **Participate in Class**: Engage actively in discussions, role-plays, and group activities to improve communication skills.

7. **Seek Help**: Don't hesitate to ask questions during class or seek extra help from teachers or tutors if you struggle with certain concepts.

By implementing these methods consistently, you can make significant improvements in your English grades.