how to get a score on common average above 70

[PerkyExpert]

my sons senior school requires 55 percent, but would like to be in a higher set as

getting a good score on all exams would put him in a higher set, what should we do?

where to start?!

What year is he in?
Get the topic lists and revision guidance for his tests, usually on the school system like Firefly / Sharepoint etc.
Go through them, make sure he knows or understands everything required.
Do any past papers that have been set.
Go through old homeworks and class tests and look at the feedback and areas to improve.

Good luck!

Common Entrance? Galore Park books but he needs to show interest and knowledge beyond answering the questions. Does he take it this year? What does his prep school feedback?