Imagine that my friend calls me and we have the conversation while I am on my way to school (I'm walking at the moment of speaking):

-Where are you?

-I am going to school.

I know that "I am going to school" means:

1. that I'm preparing to go and I probably at home yet;

2. that I'm going to school next year (to start my education).

So how to say correctly that I am on my way to school using the verb "go" and present continuous. Is it possible at all?

Thanks.