But with homework counting for no more than 10% of their grades,student can easily skip half their homework and see very little difference ontheir report cards.
请问老师，这里句子前半部分为独立主格结构，with可以省略，那样就无需连词来连接了，由于第一句已经不是一个句子了，那样这个but是用来做什么的呢？
But with homeworkcounting for no more than 10% of their grades, student can easily skip halftheir homework and see very little difference on their report cards.
你的句子前面的 but 其实是针对前文内容的转折，也就是说，在你的句子前面一定还有其他文字，你这个句子的内容与前文内容相比，出现了转折。比较：
If you want to go on a date sometime, you can ask me. But don’t count your chickens. 假如你什么时间想约我出去玩玩，那就来约我，但也不要有太大的指望。
The drinks trolley came along the aisle. Jeanne said it was too earlyfor alcohol. But Ryle overrode herobjection. 装饮料的手推车顺着通道行进。珍尼说时间还早，不到上酒的时候。但赖尔对她的反对建议不予理会。
