First, you write a list of all the things you need to do either in a day or a week - choose a time frame that suits you depending on the degree of repetition you have in your life. For most people a week will work well.
Choose how you wish to break these tasks up. You may choose - research, reading, action tasks, phone calls, social media, advertising, employee management - whatever works for you. You may choose to break things up according to where you do them - say kitchen tasks (where you cook, empty the dishwasher, do food preparation etc), office tasks (where you sort papers and do research), dining room tasks (where you make phone calls and plan / organise. You may choose to use your school subjects to break this time up.
In a week calendar broken down into segments (I suggest hour segments) place all your non negotiables. Rule out your ideal sleeping time, put in your dinner time if you have a specific time that works for you, if you have to pick kids up from school put that in. You are planning any time you have available in your week to make the most out of it. This includes planning for fun time with family or friends, exercise time as well as your work time. It is entirely up to you - you may just use this technique to make your work hours more efficient or to optimise 3 hours of study after school - how far you take it is your choice.
On the physical level - I suggest you use different colours for each type of activity as you have broken them down for yourself. It helps your brain to recognise the patterns.
As mentioned in a previous post - I suggest you study or work in concentrated blocks of 45 minutes then have a "rest" period of 5-15 minutes to move, stretch, get fresh air, water and / or a healthy snack and organise for your next concentrated time block. This may involve switching books, tidying your desk to start fresh or gathering the materials you will need for your next stint. All these activities should be considered preparation for your next stint (including the exercise, stretching etc) and should allow you to get straight down to the nitty gritty when start your timer.
Time blocking and including "rest periods" after each time slot increases your efficiency as well as improves the way your body and brain work allowing for more sustained periods of pain free and constructive work in the long run or greater amounts of free time at the end.
Giving you my honest opinion on all things health related. Keeping it real and from the heart.