If you're already a WG-10 that's going to trump any school you would have had in terms of qualifying experience/education.

However, if I were the hiring manager, I'd probably have questions if I noticed incomplete schooling. While I recognize that formal schooling does not equate to intelligence or ability (plenty of successful people were dropouts) not completing education could be cause for concern.

To me, lack of formal education could indicate some potential issues that I'd want to ferret out in the interview process: Were there extenuating circumstances that impacted this person's ability to complete formal schooling? Will lack of education impact this person's ability to do the job? Does inability to complete basic education translate to a poor work ethic? I'd think you'd want to be prepared to answer those type of questions.