This is coming from a mother
Firstly don't worry until you know what the prediction is, it could be all be fine.
Then if your History prediction is a B formulate a plan to take to a discussion with the teacher.
I had parents evening last night and we needed to get my sons Maths prediction up one more grade for him to stand a chance at university applications for Economics as Maths was integral to the courses he wants to apply for.
It took 20 minutes of discussion and wasn't an easy ride, if we just said he would work harder it wouldn't have been successful.
I went with past papers he had taken with much better results than his AS result - teacher said they weren't taken in exam condition.
We had just placed son with a private tutor for Maths help an hour a week.
He's sitting in on the year below Maths lessons when he has free periods to go over a module again.
Sons second Maths teacher was called to give an opinion and luckily he thought more highly of my sons abilities with all the other factors I've mentioned, so it was agreed that his prediction would go up a level.
So think about what case you can make ....not just you will work harder
Have you taken extra reading from the library , started independent research on the history module course work if that's been given to yet, show how enthusiastic you are about the subject, state what courses you have looked at and the entry requirements.
Good luck IF you need it.