My son is taking Cambridge A levels with subjects - Math, Physics, Chemistry, Economics and English AS levels. Is he elligible to take JEE Mains and Advance.

Below I will give the list of qualifying examination for JEE mains .
List of Qualifying Examinations (QE)
i. The final examination of the 10+2 system, conducted by any recognized central/ State Board, such as Central Board of Secondary Education, New Delhi; Council for the Indian School Certificate Examinations, New Delhi; etc. ii. Intermediate or two-year Pre-University examination conducted by a recognized Board/ University
. iii. Final examination of the two-year course of the Joint Services Wing of the National Defense Academy
iv. Senior Secondary School Examination conducted by the National Institute of Open Schooling with a minimum of five subjects.
v. Any Public School/ Board/ University examination in India or in any foreign country recognized as equivalent to the 10+2 system by the Association of Indian Universities (AIU)
. vi. Higher Secondary Certificate Vocational Examination.
vii. A Diploma recognized by AICTE or a State board of technical education of at least 3 year duration. [Only for Admission to IITs]
viii. General Certificate Education (GCE) examination (London/Cambridge/Sri Lanka) at the Advanced (A) level. [Only for Admission to IITs]
ix. High School Certificate Examination of the Cambridge University or International Baccalaureate Diploma of the International Baccalaureate Office, Geneva. [Only for Admission to IITs]
In viii it is mentioned that your son is only eligible for admissions in IITs.
And he can appear for JEE mains and advanced.