Is this legal?

[colin79666]

In a sandwich shop today and there is a notice up along the lines of:
Part time positions available. Preferably 17-20 year olds.

The owner may just be suggesting it would make a good Saturday job for a teenager but then why not just say “may suit students” rather than call out the age? I’m thinking this may be a minimum wage thing but the law prohibits discrimination on age when hiring unless they can argue they wouldn’t discriminate a candidate if they applied (but who would given the sign)...