We have had good success in the Spring. This is what we do.
Put flyers in the take home school folders
Get the flyer into the school online newsletter
Stand in the car pick up lines the day of the recruitment for the K and 1st, tell them about it
Our district has a bounce house, so we borrow that for the Saturday and hold a carnival at school with popcorn and kickball.
typically we get a full den, we talk to the parents while the kids are bouncing and get them signed up.