ground /graůnd/ verb
1. to bring to or place on the ground
2. to restrict from customary activity
3. to instruct in fundamentals
4. to connect electrically to the ground

Q:-What is the meaning of the word ground in the sentence below?
My sixth grade teacher grounded his students very well in skills like math tables and spelling by regularly holding drills and contests in class.

1. definition 1
2. definition 4
3. definition 3
4. definition 2