The match is a qualifying game for the FIRA/AER U18 European Championship, held in the Armagnac-Bigorre region of France later this month.
Sexton, who has impressed with St Mary’s College, is named in the second row alongside Donagh Lawler (St Michael’s College).
The side is captained by scrum half Luke McGrath, also of St Michael’s College.
Ireland lost to England in their opening tie in the qualifiers and need a bonus-point win against the Scots to progress.
Coach Terry McMaster admitted his side face a tough task. He said: “Scotland showed they are a team with plenty of talent by overcoming England on home soil, so it puts it into perspective as our lads need to deliver a performance against the Scots that is of the highest order.
“To put one over a strong England team in those circumstances demands respect.
“But I think there is plenty of talent in our own side.
“The key is to deliver accuracy on their individual areas and the collective will look after itself.”
IRELAND U18 SCHOOLS (v Scotland): J Fitzpatrick (Gonzaga College); C McEllin (Blackrock College), R Henshaw (Marist Athlone), C Farrell (Campbell College), C O’Halloran (CBC Cork); R Scannell (PBC Cork), L McGrath (St Michael’s College) captain; G Frayne (Clongowes Wood College), B Byrne (Clongowes Wood College), E Byrne (Clongowes Wood College), J Sexton (St. Mary’s College), D Lawler (St. Michael’s College), M Best (Campbell College), D Leavy (St. Michael’s College), R Murphy (PBC Cork).
Replacements: A Murphy (St. Michael’s College), T Ferrari (Sligo Grammar School), C Taylor (Wallace High School), L Satchwell (The King’s Hospital), B Alexander (RBAI), D Shanahan (Belvedere College), S Olding (Belfast Royal Academy), R Scholes (Campbell College).