The Frequently Asked Questions stick at the top of the section wrote:
What is the format of the SW Herts tests?
We can only say what happened in the past; the schools might change the formats without notice. Beware that they may suggest a particular publisher for practice, but this may not mean that the actual tests will be supplied by that publisher. It might be wise to practice a wide variety of types to avoid being taken by surprise. The practice tests they include in the test letter are of little use.
there are two papers, mathematics and verbal reasoning. Both papers have been standard format (i.e. written answers) for as long as anyone can remember, and working was done on the test paper. Children were not permitted to take in scrap paper.
In previous years, the maths has been from GL Assessment (formerly known as NFER Nelson), 50 questions in 50 minutes, and no more challenging than KS2 maths.
For VR, they switched from NFER to Moray House (100 questions in 45 minutes) in 2005 or 2006. Many children reported that the VR was more difficult to complete in time than the Maths. But there is a problem with Moray House papers: there's a limited number of them, and although the publishers supply them only to schools and local authorities, some copies have leaked. St Michael's in Barnet had to hurriedly set a second group of tests in 2007 because of allegations that tutors had given the very same papers to their charges for practice (see this thread). After similar problems with Moray House papers, Warwickshire have found a new source (see this thread). The SW Herts consortium might take that as a warning and look for another VR supplier.
Tests take place on the same day at all the consortium schools, with morning and afternoon sessions. Each child is allocated a test centre from the schools they named on their Common Admissions Form. On the test day, the schools take some trouble to make the candidates feel at ease. In the test room there is a short practice before the actual tests. There is a 10 minute break between tests.