Computer science isn’t learning to use excel. Computer science isn’t about understanding system administration and packet shaping. It’s not about using simulations to better understand biology.
I think K-12 schools can get confused about the difference between computer science, information technology, and educational technology. They are distinct.
Computer science is the scientific and practical approach to computation and its applications. It is the systematic study of the feasibility, structure, expression, and mechanization of the methodical procedures (or algorithms) that underlie the acquisition, representation, processing, storage, communication of, and access to information, whether such information is encoded as bits in a computer memory or transcribed in genes and protein structures in a biological cell An alternate, more succinct definition of computer science is the study of automating algorithmic processes that scale.
A computer scientist specializes in the theory of computation and the design of computational systems source here. There are many reasons K-12 schools don’t “do” computer science well. I suspect one of the larger reasons is the confusion about simple definition. I've seen "computer class" as a catch-all.
From Running on Empty comes an excellent description of why computer science is difficult to define and implement in K-12 schools: Consistent with efforts to improve “technology literacy,” states are focused almost exclusively on skill-based aspects of computing (such as using a computer in other learning activities) and have few standards on the conceptual aspects of computer science that lay the foundation for innovation and deeper study in the field (for example, develop an understanding of an algorithm).
As I learn and explore computer science in K-12 space, I would be curious to hear your thoughts about computer science in K-12.