Are there any disadvantages to taking the SAT 1 at the start of tenth grade?

If you are smart and have good retention skills of what you have learned so far, you should be fine. If you have taken advanced placement courses and have good retention skills, even better. I did it in 10th grade without issue.

Go for it. You can always retake it if you don’t like your grade. Take it as often as you want.

My oldest daughter has been taking it since 8th or 9th grade. It’s great experience, and she continues to take it each year (she’s entering 11th grade this fall), with improved scores each time. I’d say the only (minor) drawback is that it costs money each time. In my opinion, it’s been worth it for her.