Elizabeth Wilson, 41, from Fife, said she had been told by his mother that two-year-old Liam Fee had stopped going to the private nursery in Kirkcaldy.
Rachel Fee, 31, and her civil partner Nyomi Fee, 28, deny murdering Liam at a house in Fife in March 2014 and falsely blaming his death on another young boy.
Ms Wilson told the High Court in Livingston she became friendly with Rachel Fee when they both kept horses at a nearby farm.
She said she was aware Liam attended the nursery but was told by Rachel Fee he had stopped going.
Advocate Depute Alex Prentice QC, prosecuting, asked: “Did Rachel give a reason why it stopped?”
She replied: “Because they had phoned social services. There were a few issues and they called social services on them, I think.”
Ms Wilson described an occasion she saw Liam in a buggy with a blanket over his head.
Asked what Rachel Fee had said to her about this, she replied: “Don’t speak to him or look at him because he’d play up or it would upset him, or something to that effect. Just because she claimed he was autistic.”
Ms Wilson described another occasion she had been giving Rachel Fee a lift and the other woman’s phone had rung.
She said: “I think it was the health visitor. I think Liam was due for a check-up and she just said she wasn’t going to answer it.
“She didn’t want to take Liam down because he’d scratched himself and he had a few marks on his feet. I said ‘just answer the phone and take him down’.”
The accused women also deny a catalogue of allegations of wilfully ill-treating and neglecting two other young boys.
The witness also said Rachel Fee had once cancelled a lift to take one of the boys to hospital because he “had blisters on his feet which had turned to gangrene, which I thought was a bit dramatic”.
“I said ‘how has it got to that point? Did you not see his feet were bad?’”
Ms Wilson said she had been told the injuries were the result of tight plimsolls.
The couple deny all the charges. The trial continues.