Deb,
The Lancasterian at Shalesmoor was two separate schools (boys and girls) until september 1934 when the girls were moved out and it became a boys only school.
It really was a special school for children with learning difficulties and there are a lot of details in the admissions register ( available here as Elaine said)
It seems that the standard leaving age between 1901 and 1945 at the Lancasterian was 16. This at a time when the minimum legal age was 12 (1899-1918) and 14 (1918-1945). Boys and girls did leave before 16 but only with special permission. Significant numbers of pupils stayed on to 17,18, 19 20, and even a few to 21.
It seems to have been a very successful system. By far the largest majority of the children left to go to work. Someone or something called SMO (Medical Officer?) or sometimes a doctor gave permission to leave before 16. Some were transferred to other schools, including approved schools.
Despite the derogatory name of Idiot's School as I understand it was locally known, the word idiot only occurs twice in the official records.
The types of words used to describe specific conditions were blind, deaf, dumb, cripple, epilepsy, St. Vitus' dance , curvature of the spine, consumption as well as words like ineducable, too low for the school, criminal acts. However, all these were few and far between: the majority were clearly just learning difficulty. Some children were retained in Standard IV or the like. The standards were akin to the US Grades system.
I have not been able to determine the total numbers in the school but unlike typical schools the admissions are fairly evenly spread through all the months of the year
Typically up to 1934 there were about 20 new admissions per year. In September 1934, all the girls, 32 of them, were transferred to another School (Highfield) and on Oct 1st over 70 boys were transferred from Highfield to Lancasterian.
From this I estimate that the total numbers in the school at any one time was probably of the order of much less than 500, possibly less than 200.
Between 1934 and 1945 the admission rate rose to about 40 per year.
I hope that helps. I have many more details. If you have any specific questions, please ask.
Dave
PS. My thanks to Dave Noon for the ability to analyse these data in detail.