What is the name of a security classification in the US that is higher than: Top Secrete and Black Ops?

[Squid]

"Black Ops" is a name invented by a video game company. It's not an official designation.

The SEALS are not a top secret organization. They even have a website. Some of their missions are classified.

The word "secret" is not spelled "secretE"

All that being said, if you want to write a fictional story just make up a fictional name. In your story only a few people know about this group so it's not like anyone on the internet would have heard about it to tell you the name. So just make one up that sounds good to you. "Ghost Squad" or "Shadow Warriors" or some such. In reality it would probably be named something that sounds totally boring, like "Office of Efficiency Analysis" or "Sanitation and Safety Inspection Detachment".