Do you know when your most productive? I know that for me waking up early (like before 9) is a big help for how much work im going to get done that day. So i try do work between 8am and about 3-4pm with lunch and breaks in between, and i make a list of everything i want to get done and use a timer to do those tasks (i use an app called MinimaList). From either 3 or 4 depending how slow i was that day in doing work and how well i concentrated, i just spend time to relax until dinner between 6-7, then after i do a bit more work (usually revising/making revision sources/practicing exam questions/doing some reading for english) until about 9 and then chill for the rest of the night until i go to bed (:
Honeslty though its whatever works for you, and in 100% honesty i dont always manage to follow my own schedule sometimes i get no where near as much work as i'd want to, so i may spend much longer trying to finish it or try finish on weekends so i dont fall behind, or i wake up later than i'd like to and it means not being as productive throughout the day or going to bed later trying to finish what i was meant to do in that time i was sleeping. BUT, i find using lists really helpful, and breaking down tasks so its not just something like 'English 9-10, Sociology 10-11' etc. I find doing something like 'English spend 10 minutes reading chapter 1-3, spend 20 minutes annotating of that one book for that day, do the same thing for the next couple between 9-10 with breaks, 10-11 spend 10 minutes reading this chapter of the textbook, spend so long writing the notes from that chapter, spend 15 minutes summorising all those notes onto an A4 word document so you've got a summary sheet (helps with revision)' - just something like that (but obviously in notes form as a list, just breaking down the topic down so that your not tackling 'English' for so many hours a day, your tackling smaller topics in english so it doesnt seem as much and such an overwhelming task)
Its totally okay to change your schedule if its not working! Have you tried changing environements too? Like for example if you always do your work in your room at a desk have you tried doing work in a different room in your house? Like downstairs at a dinner table? Or doing work outside your house in a library or cafe?