Teachers are not physicians and cannot recommend any medical intervention, including medication for ADHD. They can suggest that a child exhibit symptoms that are associated with certain conditions, which are presumed to have a neurological basis, such as ADHD. Pediatricians, psychopharmacologists, and neurologists (those professionals who are responsible for formally diagnosing ADHD and for prescribing and monitoring medications), must rely on the objective observations of teachers and others in the school to help them make their decisions about the diagnosis, and about starting, continuing, and modifying medication. Most doctors will acknowledge that they don't get a very valid sample of a child's behavior during an office visit. They must rely on teachers and parents to work with them as a team to provide the behavioral information they need in order to consider the appropriate use and effect of medication.
The other point that's important here is that teachers must make appropriate accommodations for a child with ADHD (or any other disability) in the classroom. Medication should not be considered unless there is evidence that the school is doing all it can to provide an environment that has the structure and support that your child needs. Unfortunately, some teachers are too quick to consider (and inappropriately recommend) medication as the solution to management problems in the classroom. Ask your child's teachers to tell you what they've done to make the classroom a more successful place for your son, and to provide you and the physician with a comprehensive, objective behavioral analysis. Until you get this information, don't rush to make that doctor's appointment. If you get the sense that the teachers are not sure how to do this, ask for a consultation from the special education teacher or the school psychologist, who should be able to give you some very objective and helpful information. If those folks aren't available, ask a professional from outside the school (a private psychologist, for example) to do an observation that will help you decide what steps to take.