Complex sentence: He began attending Milton Academy, a prep boarding school in Massachusetts in Fall 1961; summering before then with his family on Martha's Vineyard, he met Danny Kortchmar, an aspiring teenage guitarist from Larchmont, New York.
Split into simpler sentences: He began attending Milton Academy, a preparatory boarding school in Massachusetts in fall 1961. Summering before then with his family on Martha's Vineyard, he met Danny Kortchmar, an aspiring teenage guitarist from Larchmont, New York.