Here's why:
* Missing Verb: The sentence lacks a main verb after "going". It's missing the verb "to" before "take".
* Incomplete Thought: It's grammatically incorrect and does not express a complete thought.
Here are two ways to fix it:
1. Adding the missing verb: "When I get home from school, I am going to take a nap."
2. Using a different structure: "I am going to take a nap when I get home from school."
Both of these options create complete sentences with a subject, verb, and a complete thought.