Difficult situation. My approach would be to be direct with your parents. Tell them straightforward what your results were, but then tell them how you're committed to improving the grades. Maybe also discuss with them any potential reasons why your grades have dropped, maybe you've been stressed lately or something has been on your mind that has caused your grades so drop. That's what I would do in your situation but at the end of the day, I don't know you or your parents so I can't predict exactly how they'd react. I wish you the best of luck but remember, even though they might be strict they still love you and likely just want to see you successful and happy in the future. Good luck!