Question: I got into an argument (with a physician friend) who thinks it’s bad to test asymptomatic kids (“flawed policy with many pitfalls”) because dead viral particles turn tests positive. What do you think? Especially with the current at home/over the counter tests we have, and the community spread in places like Houston (with no mask mandates or regular testing policy for kids, teachers).

Answer: Interesting argument.  Like most arguments, you both raise good points.  That said, I agree with you!  As requested, here are my thoughts about screening tests:

1. Testing is an important part of a layered approach for COVID prevention in schools (Table 1), especially in communities with high levels of transmission.  CDC recommends that K-12 schools use screening testing for unvaccinated staff and students as a component of safe in-person learning, particularly in areas with substantial to high levels of community transmission.  CDC further states, “Screening testing may be most valuable in areas with substantial or high community transmission levels, in areas with low vaccination coverage, and in schools where other prevention strategies are not implemented.”  Sounds like Houston!
2. Frequent screening (e.g. at least once per week) can reduce wider outbreaks and school closures. Frequent screening helps to keep transmission low and students in school. Studies indicate that frequent screening can reduce in-school infections by 50 percent. CDC recommends random sample testing (e.g. random 10% of students) or pooled testing with results available within 24 hours.
3. No test is perfect and false positives are possible.  The “dead viral particles turn tests positive” component of your friend’s argument is only applicable to PCR tests, NOT to antigen tests (like the home-based tests you mention) [see Q&A of 10/24/20].  Meanwhile, it’s actually antigen tests that are far less precise than PCR-based tests, meaning that they are more likely to give false results than PCR tests (see Q&A of 9/18/20).  It’s important that schools choose tests with high specificity to reduce the chance of false positives.  Moreover, the possibility of false positives declines dramatically for both PCR and antigen tests as underlying prevalence increases [see Q&A of 11/6/20], which is why screening testing is recommended in communities with substantial to high levels of transmission.    
4. Screening testing does not obviate the need for masking, vaccination, and other public health measures.  Again, it’s part of a layered approach!

Table 1. Screening Testing Recommendations (from CDC)