Praxis Grammatica - Qualifications for Teaching

The 17th century Praxis Grammatica tells you pretty much the opposite of yesterday's bit of wisdom:

[ 204 ] Ille qui docturus est alium prius seipsum doceat.
[Anglice (English Translation)]

• How to Pronounce Latin
• Table of Latin Pronouns
• Latin Personal Pronouns
• Latin Verb Tenses

Do you have a different interpretation? Please post in the comments about this bit of wisdom from Praxis Grammatica.