There are workbooks you can buy to help with math, reading, spelling or whatever. I'd get one of those and part of the evening routine is in the workbook. HOWEVER, if he gets good enough at the workbook pages (set your own guidelines and standards) then he doesn't have to do them any more.
Make up your own spelling tests. He may make the excuse that he can always use spell check, etc. If he has to WRITE a paper or does not have access to spell check......then what?
How well does he understand PHONICS? I know from teaching that understanding phonics is a HUGE help with spelling. Laziness sounds like part of the problem. Personally, as a teacher, mentor and coach.....laziness is NOT acceptable.
If you have to hire a tudor, do it. Sometimes kids don't want their parents helping them. Regardless, let HIM make the choice, but NOT doing it is NOT an option.