There is a school marked about ¾ mile south of Hartpury village in a survey of 1882/3,

https://maps.nls.uk/view/101453142

It’s still there in a revision of 1901/2,

https://maps.nls.uk/view/101453139

Hi Sue,
St Marys CoE Church has been in Hartpury since long before 1887, the excellent Hartpury Heritage site includes this page among many others
https://www.hartpuryheritage.org.uk/the-church/description/

The village entry on the Genuki site includes a list of past Vicars since the C14th !
http://www.genuki.org.uk/big/eng/GLS/Hartpury/Vicars

However regarding your query about 1887, there was also a strong local Methodist movement too,
http://www.hartpuryparish.org.uk/places_of_worship.html

as that's the year the foundation stone was laid for the Chapel, see
https://www.britishlistedbuildings.co.uk/101078672-hartpury-methodist-chapel-hartpury#....

This 1895 Directory states there was also a Roman Catholic Chapel, but was it there in 1878 ??..
https://ukga.org/england/Gloucestershire/towns/Hartpury.html

Apparently YES, according to this Gazetteer entry from 1872;
http://www.visionofbritain.org.uk/place/10828

It appears that Hartpury was an important bastion of the Roman Catholic Church for neighbouring Gloucester city too,

"In the late 16th and early 17th century Catholic recusancy in Gloucester almost, if not completely, disappeared and in 1676 there was said to be one papist in the city. James II sent a priest to the city but the mission gained few converts. ........ In the turmoil in the city following William of Orange's invasion the chapel was ransacked, the priest was imprisoned for a time, and Catholic houses, including that of Sir William Compton at nearby Hartpury, were attacked. The mission was ended by those events in 1688, and in 1735 only two papists were recorded at Gloucester.

Tradition states that in the early 1790s mass was said in a house in Berkeley Street used for a Catholic school. From 1790 the mission was undertaken by John Greenway (d. 1800), who bought a house in the later London Road and built a small brick chapel behind it. The chapel was registered in 1792 and had a congregation of 40 in 1813. The mission had close links with a convent established at Hartpury in the mid 1790s, and Robert Canning, who became lord of the manor of Hartpury in the early 19th century, was the mission's principal benefactor. In 1857 Frances Canning gave £1,000 for building a larger church and in 1859 the chapel was demolished and the new church, which was not oriented, was erected in an early 14th-century style to a design by Gilbert Blount."
http://www.british-history.ac.uk/vch/glos/vol4/pp317-319

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Sadly apart from snippets such as above, the excellent British History website doesn't yet include a dedicated section to just Hartpury. This is where I would have hoped to find hostory of the area's school or schools. The aforementioned Hartpury Heritage Trust Site includes more detail about the Convent, and of a boarding school "for young ladies" run by the nun's in the early 1800s, the convent closed in 1839.
https://www.hartpuryheritage.org.uk/our-initiatives/old-chapel-hall/dominican-nuns/

Sorry Sue as I suspect this probably doesn't really help you much, and may even just complicate things ?. If you still have more specific queries then we'll do our best to help,

Jeff.