You need to check their websites and email admissions if it is confusing because you are right many schools have decided to keep the ISEB as pre test or as the entrance exam because their admissions felt it was successful
I know Alleyns have decided to keep it as a pre test so this year's intake have taken it too. Emanuel didn't use ISEB last year and haven't this year. I'm not sure about Whitgift and Dulwich.
The ISEB has 4 tests: Maths, English, Verbal Reasoning and Non Verbal Reasoning
Some schools looked at different components of the exam. For example, Wimbledon High considered VR and NVR, other schools did Maths and English only etc - so good to find that out too.
I highly recommend Atom Learning from end of year 5 for familiarity and practicing these computer based tests.
Do check the websites and email the admissions department if you need to.