Long-Term GCSE Science Tutor

My son is currently working below his target level in GCSE Physics, Chemistry and Biology, yet he is determined to finish the course with A*–A grades. I want to give him consistent, expert support over the next two academic years, so I am arranging a minimum of two hours of online tuition every week... (Budget: £2 - £5 GBP, Jobs: Education & Tutoring, Educational Research, Science Tutoring, Teaching/Lecturing)