I thought of 成績 (seiseki) off the top of my head, but as Abby san and bobo san wrote, it could also be 点 (ten) or 印 (shirushi) depending on the context. Maybe you can give us an example sentence and we'll know which word is best to use.

"mark" means "印（しるし）, 印をつけること" other than "点". In Japanese schools, they use "マークシート"(marksheet, mark sensing) for examinations and questionaires.

the unit is 点。 eg. 満点 : full mark