An $800,000 Proposition 2½ override that would cost the average homeowner an additional $189 in property taxes a year will face voters at the special state election on Tuesday. The vote comes on the heels of a contentious Town Meeting during which advocates for the Whitman-Hanson Regional School District pushed hard for the town to contribute an additional $210,411 to the town’s share of the regional school district. The override also includes $515,000 to restore cuts in town budgets, according to Town Administrator Frank Lynam. Whitman-Hanson superintendent Ruth Gilbert-Whitner said the override would help keep class sizes in the elementary schools from rising above 25 students per class and relieve some of the cuts in arts, foreign language, and music instruction. Hanson defeated a similar proposal last month; both towns approved an override last year.