Subject line should be short but descriptive. Whenever a person reads a subject, he/she should know what the application is all about. In the question, the application is all about applying for a school teacher so subject must contain words for teacher.
0.75 miles of range is a low distance for a WAN (Wide Area Network) so a point-to-point WAN tehcnology such as IP-sec or SD-WAN can be preferred. But the least expensive option would be choosing IP-sec as specified in the question.
