Two men aged 39 and 32 and a 31-year-old woman from Shrewsbury were arrested on suspicion of obstructing a coroner.
This offence commonly relates to circumstances where a person conceals an unexpected death for which they may not be responsible but doing so interferes with the work of the coroner.
The three have been bailed to reappear at Shrewsbury Police Station on March 6.
Police had been given an extra 36 hours to question the three, who were originally arrested on suspicion of murder following the discovery of the body just before midnight on Sunday.
Staff and pupils returned to Harlescott Junior School on Wednesday, which was closed while police investigated the discovery of the body of a woman in her 20s in the doorway of a side entrance.
A post mortem did not confirm a cause of death and the woman's next of kin has been informed but her name has yet to be released.
Parents dropping children off at the school on Featherbed Lane expressed their shock at the latest developments.
Heather Morrant, 24, who lives off Featherbed Lane, was not able to use her usual short-cut through the grounds of Harlescott Junior School to take her children Gracie, four, and Sebastian, three, to Sundorne Infants School, while police investigated the scene.
She said: "It does change things a bit that it's not a murder inquiry but there was still someone found dead in a school playground. It's a bit worrying so close to home. I suppose things like this happen everywhere but it's a shock for it to happen in Shrewsbury because things like this don't happen here very often."
Maurice Tomley, 44, of Partridge Close, walked his daughter Chloe, eight, to Harlescott Junior School where he said parents were concerned over what had happened.
"It's a shock really and no-one knows what's happened apart from the police and the people involved," he said.
Police continue to appeal for anyone with information to call 101.