Few behaviors are more unappealing to teachers than spitting. A student might spit on school property in an effort to appear "cool" or to gain the attention of his peers. The challenge for the teacher is to stop the student from spitting, while giving minimal attention to the behavior.
Spitting on another person -- which often is a hostile act that can cause considerable distress to the target -- is a different matter, of course. You should respond to that behavior as you would if the child had hit a classmate; take firm and prompt steps to ensure that the behavior does not happen again.
WHAT YOU CAN DO
Determine whether the student's spitting has a physical basis. Frequent spitting may be due to a medical -- perhaps a bronchial -- problem. Talk with the student's parents to find out if that is the case. If so, work with them and with the student to come up with a plan for what to do when he has the need to spit. You might, for example, suggest that he carry a package of tissues with him or keep some in his desk, and provide him with a bag to keep in his desk for disposing of used tissues. If the student needs to go to the restroom to spit, arrange a signal he can use to alert you that he is going to the restroom.
Have a private talk with the student. Take the student aside and elicit his cooperation in stopping the behavior. Ask him -- in a non-judgmental way -- why he spits. Tell him that spitting is unacceptable in school, unless he has a physical need to spit, and if that is the case, he can obtain a tissue from you or get a pass to go to the restroom. Make it clear that, whatever the cause, he is not allowed to spit on school property, either inside or outside. Help the student understand that his classmates might find spitting offensive and avoid him as a result.
If the student spits on school property, have him clean it up. If the student spits on the playground, for example, have him get a pail of water and pour it on the area. If he spits on the floor, have him spray disinfectant on the area and wipe it well with paper towels. If the student continues to spit on school property, you might expand his clean-up responsibilities.
If a student spits on a classmate, take immediate action. Let the student know in a very firm manner that this behavior is unacceptable and will not be tolerated in your classroom. Insist that he apologize to the other student. You might inform the offending student's parents of the incident, perhaps by having the student call to let his parents know what he did. You also might provide a school-based consequence, such as missing a desirable school activity or staying inside during recess. If you have concerns about the health consequences for the child who was spat on, talk with the school nurse.
Help the student learn to express his anger more appropriately. If the student's spitting resulted from anger at a peer or an adult, help him find more appropriate ways of expressing anger. If the incident appears to stem from an ongoing conflict between two students, try getting them together to resolve the dispute.