I dont see any sign of your Peter on the National School teachers lists, it's dated 1905 and is held by the National Archives of Ireland.
I found the 1909 death for him in Mountmellick district, reported age 76. There's a good match for him on the 1901 census with his wife daughter and two grandchildren which I presume you have seen already, he is a School Master living at Windgate, which is just south of Bray on the road to Greystones.. A search of the c1900s OS map shows Windgates School to the south west of the townland.
Your Peter is listed in Thom's 1904, officially a 'Dublin' directory but it also lists Bray - there's an listing for Windgates in the section for Bray which an entry as follows :
Erasmus Smith's - Male and Female Schools - Peter Keegan, teacher
Peter is also listed at Windgates in the 1906 Thom's, the 1910 edition shows a Robert Kelly as teacher. I think Killane is probably a bit too rural to appear in a directory - maybe Peter might be mentioned in a newspaper ?