六年级正在进行时的句子包括：

1. What were you doing at nine last night？

2. I called you yesterday afternoon but there was no answer.

3. I was visiting a friend of mine most of the afternoon.

4. They aren't looking at the blackboard.

5. They are cleaning the classroom.

6. They are having dinner.

7. They are playing basketball now.

8. Look! My father is watching TV.

9. Look! He is doing his homework.

10. Listen! She is singing an English song.

11. No, Jack is doing his homework in the classroom.

12.晴空万里，蓝天如洗，白云悠悠，汇成一幅辽阔无垠的画卷｡

这些句子展示了现在进行时的不同用法，包括描述正在进行的动作、状态和情感。现在进行时通常由“be + 动词-ing”形式构成，例如“is watching”、“is doing”等。