Hi Allan, welcome to the forum! You are right in saying that the colliery houses are now gone but there are a couple of remnants of the place left. Howard House, the former pit manager's house, and the adjoining former Office Row, still exists but is now a school. Just a few hundred yards away is Blue House farm which was also there in the 1920s. Moving on towards Morpeth, you come to Nedderton Village where the old junior school exists, though no longer in use as such. However, I'm not sure if it was in use for the colliery children as early as the 1930s when your dad would be a 'junior'.
Second Street, Netherton Colliery consisted of 2 rows of houses: 1st Second Street and 2nd Second street, as far as 1911 at least. "nd Second street later became Plessey Street. I'd have to wade through my research for an exact date. Hower there was a Mills family living at number 13 2nd Second Street. Head of the household was Ralph Mills, born Sunderland then aged 29 and married to Rachel, also 29 . They had three children: maria, William and Thomas aged 2 months to 2 years. Only the baby was born in Netherton Colliery indicating that they recently moved to Netherton. Also living in the house was Ralph's brother William, aged 20, also born in Sunderland, Albert Gibbon, a lodger aged 21 and Barbara Scott, a 19 year old servant with roots in Netherton. Quite a crowd for 3 small rooms!
Do any of those names ring any bells?