Are you going to the school party?这句话的肯定回答可以说Yes,I will.还是应该用：Yes,I am.

Are you going to the school party?这句话的肯定回答应该用：Yes,I am.
be going to do 因为有助动词be,所以回的也用be的相应形式
遇到这种问题可以搜索 be going to 的用法,你就会查出你要的答案的,下面是我帮你查到的
三、含be going to 的句子变否定句和一般疑问句的变法
由于句子中有助动词be,因此be going to 的否定句和一般疑问句的构成很容易,即在be (am,is,are) 的后面加上not 就构成了否定句；把be (am,is,are) 放到句首,在句末加问号就构成了一般疑问句,其答语为：Yes,主语+ am/is/are./ No,主语+ isn't/aren't./ No,I'm not.不过 I am...在改为一般疑问句时常常改为“Are you .”.例如：
They are going to see the car factory next week.(肯定句)
They are not going to see the car factory next week.(否定句)
—Are they going to see the car factory next week?
—Yes,they are.(No,they aren't.) (一般疑问句及其回答)
不明白的再问哟,请及时采纳,多谢!