Base 10 blocks should be given out only after the teacher gives directions on using them and is certain the children understand the directions. Unfortunately, if they are placed on desks in advance, students have the tendency to play with them instead of paying attention. When children play with the base 10 blocks, they are noisy and distract other students who are trying to concentrate.
Furnishing children with base 10 block manipulatives is more expensive than giving them worksheets or having them draw pictures to symbolize the numbers. Additionally, throughout the year, some base 10 blocks may get lost, so they will have to be replaced. Keeping the base 10 blocks in a bin may help prevent students from losing them.
Base 10 blocks can facilitate the desire to physically count individual blocks longer than necessary. In some situations, weaker students may rely on them and have trouble making the tranistion to performing operations without them. Some students may get in the habit of drawing base 10 blocks even when a teacher does not require it. This can make finding a solution take longer.
Base 10 blocks are often given to children when they are working in groups. It is not unusual for students to misuse the blocks by building with them. Additionally, some children may throw the blocks. Thus, students can easily get off task when they are using them incorrectly.