Empirical evidence is hard to find but this quote from the pressure group Ban the Booths may tell us something:

In Scotland there is a wave of ACE [Adverse Childhood Experiences] and trauma informed practice, Government ministers talk of love and the encourage relational practice. In England we are arguing about which stick is best to beat the sin out of the child. Time for a change. We want a debate in public and in Parliament, a regulatory and accountability framework for isolation and resources for schools to move to evidence informed behaviour practice.

https://banthebooths.co.uk/blog/whybanthebooths/

In the Guardian yesterday:

Schools are converting toilet blocks and classrooms to build isolation booths to accommodate “disruptive” children, the children’s commissioner has said, as campaigners warn that excessive use of the practice could be putting young people’s mental health at risk.

https://www.theguardian.com/education/2020/jan/17/schools-converting-toilet-blocks-into-isolation-booths

The practice in Scotland seems less common. BBC UK reported in November 2018:

It learned that more than 200 schools in England used isolation booths, with 12 in Wales and six in Scotland but none in Northern Ireland. While the majority had rules for children spending a maximum of one, two or three continuous days in isolation, 225 pupils in England and one in Wales spent a whole week in isolation booths as a single punishment last year.

https://www.bbc.co.uk/news/education-46044394

Reporting Scotland were not able to worry us with the practice at any point. Had it been comparably common in Scotland, there would have been around 20 rather than 6 schools adopting the practise. Perhaps that 6 is now zero?