The phrase "a completely different school" is correct and usable in written English.
You can use it when comparing two schools or discussing a change in educational institutions that is significantly distinct from the previous one.
Example: "After transferring, I realized that I was attending a completely different school, both in terms of curriculum and culture."
Alternatives: "a totally different institution" or "an entirely different academy".
Mickelson and Stenson were not so much in a different class from everyone else as they were in a completely different school district.
"I took a big risk to leave playing baseball and go back and play football, especially at a completely different school," Wilson said.
Rich was of a completely different school.
Your teenager will probably still be living at home, albeit on a completely different school schedule than in high school.
Miramonte Elementary students will be returning to a completely different school on Thursday after their two-day hiatus from the classroom.
Lawrence said that my mistake was not understanding that handicappers and football players are from completely different schools.
Due to the high population density, neighbors will live three blocks away from each other yet their children will go to completely different schools.
During that time of being at home and enjoying the carefree, informal, learning environment, I would have never thought that today I would be able to say that I went through five completely different schooling systems leading up to college.
You might have thought that this year, in the first year of a completely different exam, schools would be a bit more cautious about their predictions and have brought them down a bit.
"You might have thought that this year, in the first year of a completely different exam, schools would be a bit more cautious about their predictions and have brought them down a bit," she said.
[A percentage of] 100 is a case of complete segregation where, say, all of the white students are attending these schools and all of the black students are attending a completely different set of schools, so there's no overlap at all," Hinrichs said.
