Not a Summer job as such but has he/you thought about NCS? Should be able to fit it in AND a Summer job too. My younger daughter did her GCSEs last year and managed to fit in 4 week NCS plus a "shop assistant" type job at M&S. She really enjoyed both and as you say, was an eye-opener for her too.
http://www.ncsyes.co.uk/what-is-ncs
Add : She still works at M&S on weekends and during holidays whilst in Sixth Form.