If you plant seeds directly into the soil, the seedlings will probably need to be thinned. Plants that grow too close together will be weak and may not produce a good crop. The seed packet will tell you how far apart the seedlings need to be for the plants to have sufficient space to mature. For example, radishes need to be thinned to be 2” apart; beets will need 4” of space, and broccoli needs 12” between plants. You will want to remove the least healthy of the seedlings.
Thinning can be a challenging task for younger students. Pulling the unwanted plants may disturb the roots of plants you want to keep. Sometimes it is better to use a a scissors to cut off the plants that are in excess.