Our students are very good and they are polite and helpful一句话中有两个and的了,算错么,如果错请帮

不算错,如果实在想改,可以这样写：
Our students are not only very good but also polite and helpful.那我不改老师肯定不会算错呗？如果改成Our students are very good 。 They are polite and helpful。是不是也行？对，这样也可以，很好。