I am exactly at your situation i am alsp grade 10 and top student, but it didnt start this year for me it started when.i was in grade 9 my results are kinda going 📉📉 and yes i think your mom is right we must learn o control our self rather than completely avoiding the phone cause after all you need a phone to call and stuff and you can`t live without a phone forever, i am still looking for ways to control my self but what i suggest you is uninstall social media shit like facebook and instagram and most importantly delete tiktok from your life permanently, you dont need it, its just compelete distraction, this is a basic tip for freedom from phone addiction. Other than that i dont know what would work for you but for me i kinda "reward" my self after doing some school work so i have something to look forward to. for example if i do math homework i would reward my self with some call of duty (my favorite game), thats becoming a habit now, and it created good balance between work and play for me, this may work for you or you may find a better approach that works for you, keep experimenting! I hope this helps 🙂