How do you deal with squabbling t(w)eens?

[FiveHoursSleep]

DD1 is 13 and DD2 is 11. They are y7 and y8 and they are horrible to each other :(
They were really good friends when younger and even a year ago, they could sit in the same room, but since DD2 started at DD1's school things have downhill.
I'd say 80% of it comes from DD1 who is embarrassed by her younger sister who is often loud, inappropriate and immature (She has ASD).
But DD2 responds by screaming, crying and lashing out.
Both of them swear and call each other names.
I tolerate disagreements but once they get nasty or physical I tend to separate them and give them housework to do.
Things are getting worse, not better, and the two smaller ones are picking up some dreadful words and behaviour.
Has anyone got any brilliant ideas or is this my life for the next 4-5 years?

Hi there. We have a sibling rivalry issue between DS1 (Y10) and DS3 (Y6). DS1 thinks DS3 is annoying, loud, babyish and not understanding enough of DS2. DS3 feels that DS1 gets too much of my attention (DS1 is recovering from a long-term illness).

Thankfully, DS2 (ASD) stays completely out of it, as does DD.

Our first strategy was to ignore it and let them sort it out between themselves. This was a disaster. Their fighting escalated to the point where they were upsetting DS2 and DD.

The next strategy was zero tolerance. This was hard work and required a lot of input. I had to physically be present if they were in the same room to keep an eye on them. In the short term, it has worked. It broke the cycle of arguing which had become habit. They have been getting on well for a couple of weeks now.

However, DS3 starts Y7 at DS1's school in September, which could well trigger all-out war.

Has the problem got worse since DD2 started at DD1's school? Adolescents can be very aware of what other people think of them. Having a sibling who is quirky or behaves unusually can make a conformist feel like everyone is judging them.

We have close family friends with a DD in the same year as DS2 (and your DD1), and she is often asked about DS2's behaviour, as if she is somehow responsible for him! They aren't even related!

TheFirst, yes definitely much worse since DD2 started at the school.
DD1's friends quite like DD2 but DD1 hates it if her younger sister so much as speaks to them.
DD2 doesn't really fit in that well with the other Y7 girls as everyone is desperate not to stand out, so all she wants is a kind word form her big sister :(

I can understand the sensitivity an older, neurotypical child feels when a younger, neurodiverse sibling joins their school. They have invested time and effort into establishing an image of themselves as being the same as everyone else and part of the 'tribe', and anything that threatens that status quo can be stressful.

When DS2 started in Y7, DS1 was in Y9. DS1 was so worried that his 'friends' would judge him for DS2's behaviour that he said he didn't want DS2 to walk with him on the way to/from school or speak to him or his group.

. Fortunately, DS1 grew out of the judgemental friends and now has much more understanding friends who all think DS2 is sweet and anyway are mature enough not to tease DS1 if DS2 does something unusual.

This, and DS1's increased maturity, have really improved the relationship between him and DS2.

Yes, I can understand why DD1 feels the way she does, but just wish she didn't have to be so nasty to her sister so much of the time :(