Mike I've rechecked the 1921 census for Rea Street South for the left hand side, the entries are:
Sheffield Works
23, 1bk 23, 25, Melbourne Place (10/9/8/8repeated/7/6/5/4/3/2/1)
47
Lydney Place (10 to 1)
53 (3 different census returns)
54
55 (2 returns)
56
Then the enumerator moved to 158 Barford Street
I may be a bit out with some of the numbers but fairly sure it's almost opposite the school