 Halloran, with help from Simeon Lord and John Macarthur, established a school for "Classical, Mathematical and Commercial Education" (also known as Sydney Grammar School).When news of this reached London obstacles were put in his way by the English authorities, but Lachlan Macquarie and Thomas Brisbane successively supported him, and he established a high reputation as a teacher.In February 1827 he applied for a grant of land for a free grammar school which he proposed to establish at Sydney.