Do not send 1st semester grades unless asked or unless the school says we release decisions in march and feel free at your discretion.
If someone sends them in (your question about two side by side kids) - and they weren’t asked for they won’t be looked at.
Schools websites will detail what they use - for many (especially the early deciders), it’s grades 9-11 and that’s it.
For those that are asked for 1st semester grades, it’s because the school is likely on the fence about them - but they’ll be asked. That’s when you send it in. Or if you are deferred and they say you can send in.