 Re: He's been working in a bank since leaving school.
The problem is not grammatical but stylistic. The use of any time expression - before, after, since etc plus the gerund is associated more with a written style than a spoken style. But all the examples I can find of since + present perfect come from spoken English - eg :
They´ve put in three new kitchens since they´ve lived there.
It´s a fairly rare construction anyway, but when it does crop up in the concordancers it seems always to come from a spoken corpus. This means that if you replace the clause with the gerund, it´s grammatically correct but sounds odd because of the stylistic conflict:
??They´ve put in three new kitchens since living there.
Can you provide any examples of since + present perfect which clearly come from contemporary written English? |