The question of whether girls were taught in the Monoux School after 1819 is a vexed one. Certainly they were not admitted to the foundation in the the Roberts regime (1820-36), or the Griggs era (c.1850-1879). The origin of the speculation here was an undated local newspaper clipping in a school scrapbook of the late 1920s, which was an obituary for a lady who is stated to have "attended as a girl the old Monoux school by St. Mary's Church". Exact dates were not given in the clipping, but her attendance must have been between 1858 and 1863. The probable explanation for this is that this girl was one of the private pupils of Mr. Griggs' daughter, noted by the inspector, Fearon, in 1866. Since Miss Griggs also taught some of the boys for French and Drawing, it is possible that joint lessons were held. Since the boy foundationers were paying mandatory fees at that time, it is quite likely that the distinction between Miss Griggs' private pupils and her father's school became a fine one.

The first major attempt to reform the school appears to have taken place in 1870, when three factors combined to make the time opportune. Firstly, the office of almspriest-schoolmaster became vacant after George Hignett, a successful applicant for the curate's post, refused to accept the job. Secondly, Henry Griggs had obviously been heavily criticised through the report of Fearon. Thirdly, in 1869, the Endowed Schools Act had become law, which provided the means to the trustees of augmenting the endowment of the school. This was Section 30 of the Act, which provided that, if certain conditions were met, the Endowed Schools Commissioners could make an order diverting to educational purposes the resources of under-used dole, apprenticeship, and miscellaneous charities. Thus it was that on 26 April 1870, a group of the Walthamstow establishment gathered in the Vestry Room to resolve that the Monoux School be converted to "a middle-class school, for which there is great need in the Parish of Walthamstow". This date is one axiomatic to Walthamstow's development, for it was the very day on which the railway reached the town, which was to lead to a complete change in its social and  demographic make-up. The group then wrote to the Commissioners to that effect, mentioning several charities that could be appropriated under Section 30 of the 1869 Act.

After the usual meetings, a draft scheme was agreed, and published in January 1873. But this scheme, and an attempt to revive it in 1877, both failed because the governors of the charities to be diverted felt unable to agree to the terms, and their concurrence was essential for the purposes of the Act. There was also a certain amount of disquiet in the town. The Working Men's Institute - one of whose officers was Henry Griggs - made objections, and very reasonable criticisms were offered by the normally-moderate Walthamstow Chronicle in its editorials in February, 1877. Griggs' own position was precarious. If either of the plans of the seventies had been accepted, the trustees had it in mind to pension him. He would certainly have lost his job, because the draft schemes insisted the master of the reformed school be a graduate. He himself knew this, for a letter still exists in the school from him referring to the first meeting between the interested gentlemen and the commissioners in May, 1870, as "determining my whole future".

As things happened, it was a combination of Griggs' death, and the regrouping of all the Walthamstow charities under single direction, that led eventually to the refoundation of the school. There is no record of the exact date of closure of the old school. Henry Griggs was paid by the trustees up to 25 November 1879. There is no exact record of his death, but Peacock says it was in 1879 or 1880. The Trustees were still advertising places in the school on 20 December 1879 and it is possible that a temporary master was engaged during 1880, but the school was certainly closed by 6 January 1881, when the Trustees leased out the rooms in the almshouse building.