To help you prepare for the written tests, we suggest that you look at some of the books recommended for GCSE or IGCSE candidates. The following list is not exhaustive, but all are textbooks recommended for our own students. Links are provided to Amazon for your convenience.

Biology
Longman Biology for IGCSE
by P Bradfield, S Potter

Chemistry
IGCSE Chemistry
by B. Earl, L.D.R. Wilford

Physics
Longman Physics for IGCSE
by B Arnold, S Woolley, P Johnson

Design and Technology
The Essentials of GCSE Design and Technology: Resistant Materials
by Brian Russell (Editor)

The Essentials of GCSE Design & Technology: Product Design
by Brian Russell

Economics
Economics for Dummies
by Peter Antonioni, Sean Masaki Flynn

Mathematics
IGCSE Mathematics
by Paul Metcalf

Those applying for Higher Level Mathematics would certainly benefit from studying:
Additional Mathematics for OCR
by Val Hanrahan