The repackaged, single-volume Dragonlance Classics 15th Anniversary campaign module defines the points of character advancement as: Defeating Khisanth in Xak Tsaroth; freeing the slaves at Pax Tharkas; defeating Verminaard in Thorbardin; defeaing Feal-Thas at Icewall; discovering the dragonlances in Dragon Mountain; facing the dragonarmy at Palanthas; ending Lorac's Nightmare in Silvanesti; discovering the dragon eggs in Sanction; and defeating the Dark Queen in Neraka.
Assume that the heroes start the campaign at, say, 4th level, that means they'd advance a level at each of those pivotal points. That puts them at 13th level by the end of the campaign, which seems about what the modules intended.