I teach it to people of all levels. The sooner the students start, the better for me, because it helps their Aikido. Our classes last an hour and a half - Aikido for the first hour and grappling for the remaining half hour. If people don't want to grapple, they can keep practicing Aikido. When we began, you talked about teaching defensive tactics to police.
Police wear very expensive uniforms and very heavy belts.
They may have to deal with more than one person at a time. So, most police say that the ground is the last place they want to go. When I do teach police grappling, I point out to them that they may be forced to go to the ground. They might have to tackle someone, or they might get tripped or pulled down. Then they have to get back up.