Visa and immigration
Questions about status of residence, and where the answers actually come from.
What visa do I need to work as an ALT?
That is decided by the Immigration Services Agency of Japan, on the facts of each case. It depends on the role, on the employer, and on the person applying, and it is not something this site can determine.
The Immigration Services Agency publishes the current statuses of residence and the conditions attached to each. A certified administrative scrivener (行政書士) advises on individual cases.
Can I work as an ALT on the status of residence I already have?
Whether an existing status of residence permits this work, and whether separate permission is needed to engage in activity outside it, is decided by the Immigration Services Agency. Nothing on this site settles it, and an answer that turned out to be wrong would be the reader's problem and not this site's.
The Immigration Services Agency answers this directly, and a certified administrative scrivener (行政書士) advises on individual cases.
Will a Board of Education sponsor a visa?
A Board that hires an ALT directly is the employing organisation for the immigration paperwork that goes with the appointment. Boards rarely take applicants who are not already in Japan, so in practice this usually applies to somebody changing employer rather than moving to the country.
What status is granted, and on what conditions, is decided by the Immigration Services Agency and not by the Board. Anything turning on the outcome is worth confirming with them, or with a certified administrative scrivener (行政書士), before relying on it.
Renewals, permanent residency, and bringing family
None of these are decided here. Renewing a status of residence or a residence card, whether time in a role counts toward permanent residency, and whether a family member can accompany somebody, are all matters for the Immigration Services Agency.
The same applies to what happens to a status when a contract ends. It depends on the individual case, and the Agency is the only place that can answer it.