This situation with facial recognition technology use in UK schools is unknown, as is the case for the amount of schools using pupils biometric fingerprints.Information Commissioner's Office (ICO), who oversees the Data Protection Act (DPA) 2018 and the General Data Protection Regulations (GDPR), that they are taking and processing children's biometric data.
As of this week it appears that North Ayrshire Council, Scotland, are in the process of implementing facial recognition in to its 9 high schools and West Lothian Council, also in Scotland, are looking at introducing facial recognition technology in its 11 high schools - a total of approximately 20,000 students.
In England there are:
Kingsmeadow Community Comprehensive School, Gateshead
Canon Slade CofE School, Bolton
Murray Park Community School, Derby - Update 20/10/21: I have been contacted by Realsmart who have stated, "Realsmart do not provide any systems that work with biometrics". I welcome more clarification on this and will post accordingly.
Langley Park School for Girls, Beckenham
...another 5,000 students and I suspect there are quite a few more schools too.