On my way home I saw some children were playing football in the street

playing

see 有两个搭配 see sb doing sth 和see sb do sth
可以这样记，前者是不常做的或是只看到过一次的，突然看到的，如你的例句；
后者是经常做的，比如“我天天看到他锻炼身体”
记住这个就行了，同类的词有很多

填playing
原句是see引导的宾语从句：把that省略掉了，整句应该是On my way home I saw that some children were playing football in the street.
下边的句子则是see带双宾语的用法哦：see sb doing sth

playing 强调当时正在发生的动作。
这种情况根本不能用played！

填一个词?
played