Rikki was supposed to have been in class on the day he was allegedly strangled by an older boy and left naked in woods near his Peterborough home in November 1994.
The little boy’s mother Ruth Neave was originally accused of his murder but was cleared after a trial.
A DNA breakthrough in the case more than 20 years later led to charges against James Watson, a local boy who was 13 at the time, the Old Bailey has heard.
On Wednesday, Rikki’s head teacher at Welland County Primary School described a phone call with Ms Neave in the wake of his death.
Jennifer Boxall told jurors: “She was very, very abusive. I think she basically accused me of facilitating Rikki’s murder.
“(She said) ‘He should be in school. Why didn’t you let me know he was not in school?’”
Ms Boxall went on: “Ruth Neave never brought Rikki to school, ever. She was very abusive, really horrible language.”
Prosecutor John Price QC said: “The basis of her complaint was the school had not told her he had not arrived at school on the day he went missing. Did she threaten to get a solicitor?”
The witness replied: “She did.”
Mr Price said: “Some of the language was shocking, did she call you a slag?”
Ms Boxall agreed and added that she could not reason with her even though social services were always closely involved.
The witness told jurors she had several meetings with Ms Neave about Rikki’s attendance and arranging his free school meals.
She said he was generally good at going to school but was often late arriving in the morning.
She said: “He would tell me he was late because his mother was asleep on the settee and he had to get his own breakfast.
“He also told me several times he had to make his own tea – the afternoon meal – as well.
“With regards to breakfast I’m not sure he would not have any breakfast or he had to get his own.”
Ms Boxall also described concern that Rikki was planning to run away with his sister who was in foster care but went to the same school.
On one occasion, Rikki came to school crying accompanied by his “agitated” mother, the court heard.
The witness said: “She said Rikki did not want to come to school and he did not like school.
“I calmed Rikki down, cheered him up and took him to his class.”
The last time she saw Rikki was the Friday before his disappearance in the school dining room.
Rikki’s friend Martin Careswell told jurors how they used to play in the woods where he was found dead.
He told jurors they would do typical “boy’s stuff” like catching frogs, chasing each other with sticks and making dens.
Mr Careswell said they played in the woods between 10 or 15 times but never after dark.
Watson, now aged 40, of no fixed address, has denied Rikki’s murder and the trial continues.