Oregon requires standardized testing at 3rd, 5th, 8th and 10th grades. There are a couple of test options. You can do the test in a group setting or do private testing through an approved tester.
Scores above the 15th percentile are acceptable.
If your child scores below the 15th percentile they must retest the next year. If they score lower than the state might want to have you work with someone to help the child improve.
If your child has a learning disability you can make an EDP (educational development plan) for them and let the state know that they are following the plan and meeting their goals.
A child has to be in school by the time they are 6 before September 1. You can choose K or 1st grade. I claimed my child was in K even though we were doing 1st grade just so we’d have an extra year before testing was required.
Look up the law on HSLDA for any further details. It explains it well and tells you what info has to be given the state with your intent to homeschool letter. You only have to notify the state once unless you move to a different county.