Do you think this is a right choice?

Ok so my brother is going to be in 9th grade at an all boys school. So basically last year he was 8th grade and I was 7th grade. We both transferred to a religious private school at 7 th grade. He has this friend/ best friend same age/ school/ and grade. Ever since my first day at st. Theresa (starting as a 7th grader, my bro and his friend already in 8th grade) he was really nice to me. My brother didn't like me talking-to his friends because their in 8th grade and I'm in 7th grade so it's awkward. I told his friend we can't talk to each other at school so we only talk on facebook, and everyday since him and my brother have basketball practice I see him for 15 sec. ( we basically pass each other in the hallway and we hug then walk away). But, that was in the beginning of the year. Now it's summer and I'm gonna be 8th grade while him and my bro are gonna be in a different religious high school. We planned to only stay best friends until I'm in 9th grade, so my brother doesn't suspect anything. IS THAT A RIGHT DECISION? WHAT WOULD YOU DO?