Teachers certified in one state may not be eligible for certification in another state because each state has its own set of criteria for teacher certification. A teacher seeking employment in any state will need at the very least a bachelor's degree, but the requirements after that will vary, depending on several factors. Moreover, while no state requires a master's degree to start teaching as of March 2010, several states do require that teachers begin working toward that degree soon after signing their first teaching contract.

Master's Degree Required

As of March 2010, brand-new K-12 teachers are not required to have a master's degree in any state when they start teaching. A shortage of teachers in this economy has even caused some states to relax their requirements that new teachers begin their master's studies shortly after starting to teach. Some states will accept a master's degree in lieu of a traditional four-year undergraduate degree if they allow alternative certification routes such as additional coursework.

Earn the Master's in a Certain Time Frame

In Ohio, New York and Massachusetts, all elementary and secondary teachers are required to complete their master's degrees in education within five years after signing their first teaching contract. Not all states will help pay for the additional schooling, especially if it is not required; however states with a requirement in place may offer some reimbursement.

Master's Degree for Certain Subjects

Teachers in almost every K-12 system who teach specialized classes such as special education are required to hold a master's degree before working with disabled students, as are school counselors—both specialized areas where the students need more one-on-one instruction or with interaction tailored specifically to the student, therefore requiring a higher degree.

Continuing Education and Teachers

States such as Minnesota impose no requirement to complete a master's degree; however, most teachers in Minnesota hold master's degrees because they are required to continue their education. Most states do require continuing education, which results in completion of master's degrees, even when they are not required.

Additional Salary for Additional Education

While most states do not have a specific requirement that teachers complete a master's degree, some states offer increased salary incentives to those teachers who do have master's degrees due to a widely accepted perception that teachers with graduate degrees make better instructors.