The Lawrence Arts Center’s preschool program celebrated its 20th anniversary Tuesday evening with an ice cream social at Centennial Park.

More than 150 parents and children gathered at the park to visit, play on the playground equipment and decorate T-shirts.

In its 20 years, the program has grown from one class with 18 children to seven classes with 140 children. It’s also moved from the former public library building at Ninth and Vermont Streets to a new building at 940 N.H.

Preschool director Linda Reimond, who has been with the school since its inception, said the program emphasizes creativity, problem-solving and hands-on learning for children.