So (that)they can look forward to coming home during breaks is helpful因为加上that此句就为一主语从句,从句的谓语是系动词is后面的helpful是表语.没有that前面就是错的.因为系动词前就是主语,句子做就是从句就要有引导词.如
That he came late again make his teacher angry.句子为主从复合句,前面是主语从句要有引导词.主语从句前的that可以省吗不可以。它虽然无词义无成份但不能省略。否则就不是从句了。那上面那句话是不是就是错的你的那个句子是错的加上that是对的。