In the Bible you can not see the word Sunday school.
Ephesians 4:11 tells us that Jesus gave gifts to men, some apostles, some pastors, some evangelists and some teachers.
Being a teacher of God word is a day to day activity. Not only on sundays.
2 Timothy 3:7 say we should keep learning and not be like those of the world that are ignorant.
Thanks.
This is my video below ;
This is the link to brother Eli's video