The Wallace school in Montpelier Road was a very posh ladies' school.
There is no problem tracing another pair who were there in 1851, E A and E M Rigden, age 13 and 11, both born Faversham, Kent.
They were Elizabeth Anne, and Emma Martha, baptized at Faversham, and their parents were William Rigden and his wife Catherine (nee Simpson)
William and Catherine were at home in Faversham in 1851, with their youngest daughter Augusta, 2.
Plus a visitor, a "lady"
Five house servants
And a coachman!
So it should not be too difficult to find G Humphrey, age 16, and E A Humphrey, age 14, born Southampton. Especially as G was not a common first initial for a female.
Instead of which, it seems to be impossible!
I think there might have been a mistake, could their name have meant to be
LampreyBaptism of Georgina Mary Lamprey, 4 Nov 1834, Southampton
https://www.familysearch.org/ark:/61903/1:1:QGQL-Z34ZBaptism of Emily Augusta Lamprey, 24 May 1836, Southampton
https://www.familysearch.org/ark:/61903/1:1:QGQL-Z3SJThey are attached on there to a tree which doesn't have them in 1851.
In Eling, Hampshire, in 1841.
Emily Lamprey is in the later census, unmarried. Variously described as fund holder, annuitant, private means, etc.