In the early 1900s when I was at school, the average number of children in a class was 60.
In spite of the large classes, the teacher could easily see the pupils at the back of the class because the room was tiered - or 'raked' like a lecture theatre. There is a large photo of a tiered or raked classroom.
The teacher sat at a specially high desk which had its own high chair, so that she could look out over the whole of the class. I say 'she' because girls and boys were taught separately, the boys by men teachers and we girls by women teachers.
All the women teachers were spinsters. Marriage was regarded as a full-time commitment; so when a woman teacher married, she had to give up teaching. All that changed during the wars when women had to take on the jobs of the men who were overseas fighting at the front.
Teachers seldom walked around. They generally spoke while sitting at the high desk.
When the teacher wanted to show us something, like letters to copy or sums to do, she wrote with chalk on a large blackboard.
As the floors were tiered we could easily see the board from the back of the classroom.
When the teacher had finished with the blackboard or needed more space, one of the children would be told to clean it with a duster. Fortunately it cleaned easily because the dry chalk just rubbed off. With a lot of writing or a dirty duster, though, there could be quite a cloud of chalk dust which got up our noses if we were sitting near the front.
When we started school, we small children sat on benches, but in later years we were supplied with desks.
For the younger classes, the desk seats were flat planks of wood which were attached to the body of the desk and on some desks they folded up to make it easier to get in and out.
The oldest (and largest) children had chairs but the desks themselves were essentially the same. I suspect that all the children had chairs in private schools which charged fees, but I can't be sure.
All the desks had lids to lean on while reading or writing. The design was ideal as we had somewhere to keep our pencil boxes, etc. which in turn gave us a sense of belonging in 'our' classroom.
There was a coal fire in each classroom in winter. All the fireplaces had to be cleaned, which was a the job of the caretaker. Every winter evening he would also have to fill each coal scuttle with coal and firewood. Old exercise books were used for paper. One of my teachers hid away some of the coal in a cupboard on mild days for use later when it was cold, but when the headmistress found out, the teacher was reprimanded.