I'm a very strong supporter of Church or Sunday School, or Catechism, because of my exceptionally positive experience with it, mostly at Sts. Constantine & Helen Cathedral in Cleveland Heights, Ohio, during the priestly tenure of Fr. Peter N. Kyriakos, Archdiocesan Vicar, of Blessed Memory, during the 1960's. There are 4 teachers who stand out in my life for what they taught me; I'm 59 years old. My experience was a great foundation for my own study as an adult (actually, my adult "born again" experience occurred when I was a junior in high school and my priest presented me with a Sunday School graduation gift, an explanation of the Divine Liturgy, which was well translated (the best in the GOAA) and the explanation was written by Fr. George Papadeas, of Blessed Memory. At the same time, the church was migrating to more use of the English language. I attended a new church in our area, that was meeting in an old city hall, and when I heard the "Consecration" in English, the Holy Spirit came down upon me; this church became my parish to this day where I am an Assistant Chanter, have been accorded the Official Title of Ecclesiarch by Bishop Maximos of Pittsburgh, and serve on the Parish Council. Sunday School gave me the basis for me to understand the books I read to study our faith as a young adult.
I recall my Father of Blessed Memory telling me often how lucky I was to be attending Sunday School because he didn't have that experience when he was growing up, only benefiting from some ecclesiastical course work as a part of Greek School, taught in Greek. He always routinely made me tell him and my family of what I studied in Sunday School, and he typically was enlightened by what I was speaking about.
I have taught Sunday School too. I couldn't more strongly support our Sunday School system as the basis for a student's life experience in Christ and His Holy Church. (It disgusts me to hear that there are Orthodox Churches that do not use the Sunday School materials from the Holy Archdiocese Religious Education Dept., those of OCEC, or those of the other jurisdictions.)
Maybe if you have such an issue with him missing Orthros, you can pick a year like the 6th Grade and you keep him out of Sunday School.
Another option might be to talk your Priest and Parish Council into convening Sunday School following Holy Communion.
I doubt how much a youth will understand from Orthros, though it certainly is good practice to teach attendance at Orthros.
And, remember too, if he attends Sunday School, when you get home, you can run through with him the various hymns of the day from Orthros that describe the themes of the day.
Best wishes as you evaluate the best course of action for your son's spiritual growth.
P.S. I'm single and do not have children.