▁of ▁three ▁years ▁of ▁pre - school ▁education , ▁which ▁are ▁mand atory ▁before ▁elementary ▁school . ▁Pre vious ▁nur ser y ▁is ▁optional ▁and ▁may ▁be ▁offered ▁in ▁either ▁private ▁schools ▁or ▁public ▁schools . ▁ ▁At ▁private ▁schools , ▁kind ers ▁usually ▁consist ▁of ▁three ▁gr ades , ▁and ▁a ▁fourth ▁one ▁may ▁be ▁added ▁for ▁nur ser y . ▁The ▁fourth ▁one ▁is ▁called ▁mat ernal . ▁It ▁goes ▁before ▁the ▁other ▁three ▁years ▁and ▁is ▁not ▁oblig atory . ▁While ▁the ▁first ▁grade ▁is ▁a ▁play group , ▁the ▁other ▁two ▁are ▁of ▁class room ▁education . ▁ ▁In ▁ 2 0 0 2 , ▁the ▁Congress ▁of ▁the ▁Union ▁approved ▁the ▁Law ▁of ▁O bl ig atory ▁Pre - school ing , ▁which ▁made ▁pre - school ▁education ▁for ▁three ▁to ▁six - year - olds ▁oblig atory , ▁and ▁placed ▁it ▁under ▁the ▁aus p ices ▁of ▁the ▁federal ▁and ▁state ▁minist ries ▁of ▁education . ▁ ▁Mong olia ▁ ▁In ▁Mong olia , ▁kind erg arten ▁is ▁known ▁as ▁" ц э ц э р л э г " ▁or ▁t set ser leg . ▁As ▁of ▁September ▁ 2 0 1 3 , ▁there ▁are ▁approximately ▁ 1 5 2 ▁kind er gart ens ▁registered ▁in ▁the ▁country . ▁From ▁those ▁ 1 5 2 ▁kind er gart ens , ▁ 1 4 2 ▁are ▁state ▁owned . ▁Children ▁begin ▁kind erg arten ▁at ▁the ▁age ▁of ▁ 2 ▁and ▁finish ▁it ▁by ▁ 5