What would be the Negative form of this sentence?

I am not going to school.

First. In the second one you are emphasizing the point you are going to school and won't go anywhere else

I am not going to school. The second option you gave “I am not going to anywhere but school.” Means that you will be going to school only and no where else.

I am not going to school. The second sentence is also affirmative, in a convoluted way. I'm not sure if it's grammatically correct, but the "to anywhere" definitely sounds weird. If this is what you meant, it'd be "I am not going anywhere but school". Definitely going to school and nowhere else.

*I'm going anywhere but the school* might be what you were looking for for the second sentence.

>I am not going to anywhere but school. There's a double negation here, so it doesn't affect the meaning of the sentence. You could say "I am going anywhere but school" While technically it means that you're not going to school, the meaning is slightly different to "I'm not going to school".

The negative form of "going" is "not going". Keep it simple. The second sentence can be confusing. If you did want to say that, it'd be better to say > I am not going anywhere EXCEPT school.

I am not going to school

"I am not going to school." The second sentence isn't a direct negation of the original sentence.

I am going to school’s antonym is I am (or I’m) not going to school, the second is incorrect, I am/I’m not going anywhere but school (no to before anywhere) means I am only going to school and nowhere else, which goes back to the affirmative but is more specific about your day in general

I am not going to school means the opposite of the affirmative. I am not going to (go) anywhere but school is actually not the negative but instead a more specific statement. You ARE going to school, and you won’t go anywhere else.

"I am not going to school" would mean the opposite of "I am going to school." "I am not going anywhere but school" would mean roughly the same thing as "I am going to school." The only difference is that now that are assuring whoever they're talking to that they are only going to school and nowhere else.