Archaeologists have discovered a trove of rare artifacts used by children at the site of a new development in London.

While preparing for construction, researchers unearthed several marbles, a pencil and a fragment of a reusable slate tablet with letters scratched into the surface.

“We don’t often find archaeological objects we can directly link to children, but here we were delighted to find evidence for both schoolwork and play,” according to a January 12 update from the Museum of London Archaeology (MOLA), which is leading the dig.

The marbles—some of which are still covered in colorful decorations—are what’s known as “ceramic alleys,” or small, smooth spheres designed to look like they were made from alabaster. They were discovered in a covered, brick-lined drain, which suggests they may have been lost during “a breaktime game,” per MOLA.