I don't think you understand what a colloquialism is

✨The more you know✨

Actually the much more likely meaning is that because it was considered to be inviting bad luck to wish someone good luck, you'd instead wish them something bad instead.

While yes, it does mean taking a bow, there is another meaning. Also originating in theater, actors being superstitious and all thought that by inviting bad luck they would have good luck. Though it doesn't necessarily have to be used for theater. In this case though I think OP was using it more sarcastically than anything. Or just wanting his brother to have good luck.

The term goes back to the days of Vaudeville where time was valuable and not everyone could go on stage. At some shows, acts would line up at the side of the stage (called a leg). If they made it past a certain point it was guaranteed that their act would go on stage. This was called 'breaking a leg'. The term "break a leg" came to mean "I hope you make it on stage" and in time "Good luck". It was seen as bad form to say anything other than "break a leg"/"I hope you make it on stage". So, in this case, "break a leg" could mean "I hope you make it off the bench".

Glad someone knows why we say that. I was a theatre nerd all through high school. Drives me crazy when people don't understand it

Maybe each school caters to different interests? Like one might have a really good math program and the other might have an amazing marching band. Just a few examples. Kids are all unique and schools should ideally be chosen because it is what is best for each individual child rather than convenience for the parents or just a matter of "siblings should go to the same school." I'm just guessing of course.

They could also be step or half brothers who live with different parents, or one could live with each divorced parent.

well my nephew's attend different schools. one is in a French program and the other school doesn't. same with my siblings. one attended a Catholic schools and the other in a school with an excellent math and science program. different interests, you know?

In my county, we have these programs called Specialty Centers that you apply for your 8th grade year. Each Speciality Center has a different focus and only accepts about 100 students per class. For example, one could be for Health Science (My rival), Mathematics & Science (My school), Technology (Another rival), Performing arts, etc.

My brother and I go do different high schools because the one I'm at has tech program while the one my brother is at doesnt

If the rezoning was just done and one is a senior, they get to keep going to their school, while if another is younger than a senior, they will be forced to move. This is how it's done in my county so I'm just guessing it could be the same for them.

boy, divorced parents maybe?

My twin brother and I went to different specialty high schools and attend different universities. That could be the case here or they could even live in different areas. You never know

In a lot of places "break a leg" is used in any situation where you want to inadvertently wish someone good luck.

...are you serious, 15? Are you seriously saying that OP deserves to have a broken leg over a choice of words? Granted, I myself made a joke about that, but a joke was all it was. What the hell is wrong with you?

soccer isnt a contact sport, you can tell by the way the players fall, flailing to the ground crying when you bump into them