The term “managed out” is an oversimplification, and references to specific incidents don't give the full picture. There are a number of things going on:
If a child’s behaviour is putting them at risk of permanent exclusion then, with the consent of parents, local heads contact each other to try and arrange a “managed move”. There is a formal process with some negotiation, but all schools take an approximately equal number of managed moves. It is sometimes enough to turn a child’s behaviour around.
If a child is permanently excluded, the local authority will offer them a place in another school. Unless they are lucky with timing, this is usually in a “less popular” school because all the other schools are full. I expect this is what is being referred to in relation to TS. However, if it is a second exclusion, or if the exclusion offence was serious enough to suggest the child might put others in danger, the Head of the newly offered school can block the move and refer the child to the Fair Access process. Then a committee of local heads will collectively decide where the child should go, making sure each school takes its fair share of such cases.
All of the above is complicated by the fact that there are many children with special educational, social or health needs, who struggle in mainstream secondary schools. Schools don’t have enough funding to give them the specialist support they need, and there aren’t enough places in specialist schools or alternative provision.
Having said all that, TS has very many children from its local community who are happy there and thrive. If you look in the right place, you may find their parents online. Or you may just need to visit the school to make your own judgement.
If you do find lots of recent threads on Mumsnet which criticise TS, look closely, as it is often the same people posting on multiple thread. Some people have louder voices than others, but that doesn't mean other opinions aren't out there.