Hey
I know where you're coming from. I also procrastinate when I don't want to or feel like doing school work and find that I end up rushing assignments last minute. However I have found some techniques that do work for me (sometimes) when I have to do my homework. Some techniques that I find can work like making a list and rewarding yourself. You have probably hear of this all before but if not
First I find making a list and saying to myself that I have to complete it by the end of the day can be helpful, but lots of people think ok lets make a big list and get everything out the way in 2 hours which isn't going to work. If you make a list make it a small list with specific tasks. Also try include tasks that you want to do as well, if that be watching tv, playing a sport or instrument or just whatever is your thing you know..
e.g. math worksheet, read a chapter for English, complete introduction of assignment, play guitar, read book for pleasure etc..
Then set everything out with breaks (make sure its all achievable). In your first hour you could do the math and the English, then have a break and do something you want for 15 minutes or so, then keep going.
To me when I do make the list I always feel like I am getting stuff done because I can see what I cross off and I know why I want to do the homework so I can do the fun stuff later.
Also you can reward yourself for doing certain tasks, if you really don't like math then after math have a longer break or some chocolate or whatever you like. This can help to motivate you and if you continue to reward yourself for math, after a few weeks you could slowly reduce the reward and eventually you would be able to do math without the need for a reward.
I also find for myself that motivation is one of the biggest factors when it comes to procrastination. If I am really motivated for a task then I am more likely to do it, I know it is hard to be motivated to do school work. If you want to go to university you could try to use that as motivation or even try to compete with a sibling (in a friendly way) if that will help you get motivated.
But what you could do is try a few different methods (try Google some) and find what works for you because what works for me might not work for you.
Anyway sorry for writing so much and sure ill pray for you

Hope I helped
