My DD's timetable is below, it shows the number of sessions. This includes homework but they barely get any now and if they do it's usually revision / past papers.
Sessions vary from 30 to 45 minutes, depending on subject. She is taking 9 GCSEs and the Add Maths FSMQ exam. Friday is her easy day as they finish school as 2pm and she only does Art, drawing or painting with headsets on.
She plans to take Bio-Chem-Maths-FM at A-levels. She is doing 2 sessions per week for each of Eng Lit, Eng Lang, History, German, 3 per week for Biology, Chemistry, Physics, Maths, Add Maths, and 4 for Art. (Art is time consuming but that counts as relaxation for her).
Mon 3
Tue 2 + athletics
Wed 4
Thu 4
Fri 2
Sat 6 + tennis
Sun 6 + athletics
Oh, and I created two rules which we try to stick to:
Mon-Thu no study after 9pm and Fri-Sun no study after 5pm (sees friends).
No phone checking during sessions.