Many translation versions use the word disqualified, since teachers are to exercise spiritual discipline for effectiveness in ministry.
NT:96
<START GREEK>a)do/kimo$
<END GREEK> adokimos (ad-ok'-ee-mos); from NT:1 (as a negative particle) and NT:1384; unapproved, i.e. rejected; by implication, worthless (literally or morally):
KJV - castaway, rejected, reprobate.
(Biblesoft's New Exhaustive Strong's Numbers and Concordance)