ha ha ha... LOL
if youre really smart and top notch A+ in yr 10... i think you'll do fine but if you're not... would suggest to reconsider
3Unit maths:
oh boy, you'll be doing 1-3 exercises per day (idk but in my ext class before we did examples for 40mins and 20mins to get through 3 exercises) and when you have period 0 or 4 maths class in a week and the homework piles up... yeah, its like a magical kingdom where you do maths 24/7. i dropped 3Unit cause it was too fast but mainly focus on the 2U stuff more than ext if youre up for it
Chemisty:
lots of sheets be flying everywhere for me.
Bio:
lots and lots and lots of notes. basically everything links together
physics:
boy.. so much formulas and more maths
goodluck thats all i can say XD
but if youre really dedicated into studying and you get decent scores then everything is fine