The screen was lit up for Today's arithmetic lesson.

Here are the answers to the questions based on the provided passage:

1. The screen was lit up for Today's arithmetic lesson.

2. The mechanical teacher asked Margie to insert yesterday's homework in the proper slot.

3. The word from the passage which means "put into" is insert.

4. Margie was thinking about the old schools that existed when her grandfather's grandfather was a little boy.