It is known to all that he is a good student.这里的that可以省略吗?

It is known to all that he is a good student.这里的that可以省略吗?
我知道要是变成
That he is a good student is known to all.这时候that不能省略的.
That he is a good student是个主语从句，答同位语的全错！
前面都没有the news,the fact，和谁同床？
再说，这个句子不是复制的，我自己写的。只是不清楚THAT可以省略否？