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Unlikely we can locate school records from the 1850s in Kilshalvy.
I searched the subscription site Roots Ireland and only found one likely baptismal record for one of the seven siblings and it was for Michael in 1842 rather than the 1847 in your message. Mother was Catherine McGloin. I have a link to the parish register for Kilshalvy from 1842-1877 https://registers.nli.ie/parishes/0124 There is an annotation that the records prior to 1852 are not all there and I looked at the register and it is pretty hard to read in the early years. The record for Michael shows that the family was living in Cough townland (actually Coagh) and the 1858 Griffiths Valuation shows a John Healy in Coagh in Kilshalvy civil parish. There was also a Dominick Healy in Coagh likely a relation.
I did locate the death record for Roger Healy in 1910 and the informant was his brother in law John Meehan. I also located the 1901 and 1911 census record for the John Meehan family. Not sure when Roger Healy came back to Ireland but I cannot locate him in Sligo in the 1901 census. I did not find the death records for John and Catherine Healy but images are only available starting 1878 as of now.
Name:Michael HealyDate of Birth:
Date of Baptism:13-Aug-1842Address:CoughParish/District:KILSHALVEY KILTURRAGender:MaleCountyCo. Sligo
Father:John HealyMother:Catherine McgloinOccupation:
Sponsor 1 /
Informant 1:Dominick Healy Sponsor 2 /
Informant 2:Bridget Mcglocklin
Let me know if you have any questions.