This sounds like every ten year old I know. Here, in Scotland, it seems that high school and the change to pens from pencils and the need to write longer reports ect improves both spelling and grammar. Some people never get out of spelling phonetically either and that is okay. Check everything official of course but for me it matters more that your answers make sense and show you understand the topic than your way off point answer is spelled perfectly and written properly. I also think before the ages of 11 or 12, there is a lot of 'this is how you write' and trying to make everyone write the same way when no one actually does.