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Past questions.

Extensive and intensive exposure to past questions. Look for a good series.

For jamb preparation Lamlad Physics and Chemistry is pretty cool The Invisible Teacher is good for Use of English Integrated Mathematics for Mathematics by Afolabi

For chemistry:
New school chemistry (ababio)
Lamlad chemistry.
Calculations in chemistry for senior secondary (#900)
With Jamb chemistry past question.

For physics
New school physics
Calculations in physics for senior secondary
And Jamb physics past question.

For English
Invisible teacher by dele ashade
Jamb A-Z Use of English
And Jamb englisE past question.


Get him these, am sure he would smash Jamb after reading them very well.
I used them too.