What are the different tiers of CS schools in employers' eyes?

I worked at Facebook for a long time and was involved in university recruiting. They pretty much went down the top 15ish list and had a recruiter dedicated to each school at the time. They would sprinkle in or double down on schools that had strong alumni at Facebook already, and those alumni would help recruit there. More recently though they have spread out to more schools. There is also a lot of demographic trends focusing on these schools, so they also make an effort to recruit at schools with students of a wider range of demographic backgrounds that might not be in the "top 15" lists but have strong programs. Any of these top 15 schools will give you access to these on campus recruiters, starting with internships, and building a strong resume for a competitive new grad offer process. I would say that the top four (MIT, CMU, Stanford, Cal) will get the most attention from these top company recruiters, but finding the right school for you of the top 15 will be more important in finding a job.