Its not a guaranteed process but to state it's "almost impossible" is completely wrong.
Yes, each application is dealt with based on its own merits, but I know an awful lot more folks who have been successful than those who have been refused - And this covers settlement/spouse, student & student visitor visas.
To the original poster - yes, it is possible for a Turkish National to obtain a student visa *and* have permission to work; however, they will need to be enrolled in a recognised school or college - at least that's how it was last year. I know there have been changes to the criteria for schools and colleges to be accepted as genuine so best check up on that.
They may be able to get a Student Visitor visa easier, it doesn't allow working and the education attendance criteria is a bit looser. I'm not sure, but I think the maximum stay may be six months only.
JF