school visit; outreach class
A lesson or lecture given by a visiting instructor at a school, often as part of an outreach program.
A university professor gave an outreach class at a high school.
Next week, I will give a school visit lesson at a local elementary school.
Similar meaning, but 出前授業 often implies a more informal or one-off visit, while 出張授業 can be part of a regular outreach program.
Compound of 出張 (business trip, visit) and 授業 (class, lesson). The term describes a class conducted by an instructor who travels to the students' location.