Take a look at the overcrowded cells here.
Planting precise quantities of small seeds is a good exercise in small motor skills and counting for the children. As you can see, it's a challenge! I find the most successful cell pack planting comes with larger seeds like peas or beans, ones the children can carefully keep track of as they lay them in the soil.
However, our garden grows all kinds of plants, so I challenge the children to try planting "just a few" when it comes to tiny seeds like lettuce.
When the seeds are too crowded I liken it to sharing a chair with a dozen other children. There would just be too many children to get any drawing, eating, or chopping done. Bodies would be this way and that, all struggling to find support from that one chair.
This is similar to how the lettuce plants must scratch it out if they are planted too closely. Their roots get tangled, there is competition for food and water, and plants that can't stretch and grow end up stunted.
I showed K2 this cell pack when they came back to the garden today. The children remembered planting the lettuce seeds in January and were surprised to see just how many seeds fell into one hole and none into another! Looking at a lopsided cell pack like this is a great way for the kids to remember how to spread the seeds out better the next time. When we plant small seeds again, I can refer to the crowded cell where the lettuce plants were fighting to share just one seat at the table.