If he is a kindergartener eagerly reading at or above a second grade level and doing math at or above a 5th grade level, it is highly likely he is gifted. Send a letter requesting in writing all testing results from that charter school.

It is possible he had an off day or didn't connect with the tester. It is possible he has 2E issues. It is possible that his cousins also had 2E issues and developed a way to compensate for them by 3rd grade.

Is English his 1st language? That may have an impact too.

If they administered an oral test that may not have accurately assessed his full potential given that you say he can read fluently.

I understand you have been working with a speech pathologist. Has his hearing been checked by a professional?