he said to me ,"we are cleaning our classroom ."(改为主从复合句) I ＿　＿ that thier classroom __　__

需要解析

was told were being cleaned都换成被动语态了，前面是因为主语和宾语交换了位置，后面用的是现在进行时的被动语态

he said to me ,"we are cleaning our classroom ."(改为主从复合句) I was told that thier classroom was being cleaned.

he said to me ,"we are cleaning our classroom ."(改为主从复合句)  I ＿　＿ that thier classroom __　__ __.　

我认为这个句子有问题，因为不可能有I的，原来的是He 的。所以我自己改为：He told me that was being cleaned. 不需要解释，这是直接引语变为简接引语的，不过你把主动变为被动而已