This is my best suggestion for castings for the SR Schools to the LBSC 'Girton' design allowing for the undersized wheels specified in the design.

DRIVING WHEELS: LBSC GIRTON DESIGN diameter is 2½" = 63.5mm
Scale 6'7" wheels should be 65.8mm dia. 63.5 mm is 2.3mm less and would be just about within the limits of allowable wear, but the tyres would look noticeably thin.

I suggest using Great Central class 9P 7'9" drivers at 32:1 = 63.7mm
Pin at 13" is same as Schools (1½" more than Girton)
Hub is out 2" from the tyre which is same as Girton
The weights look about right.
Main difference is in having 20 spokes instead of 22 in Schools, though less noticeable on smaller wheels.

LEADING WHEELS: nearest casting is P19 is a 10 spoke wheel made for 32:1 GWR Kings.

TENDER: nearest casting is T78 for the tender. This casting normally has allowance for 2¼" hub out from the tyre.