My classmate said I am 'less'

Simply ignore them no matter it is true or not.

Concentrate your study and show them who you are.

Be yourself. You don't need to change yourself to please the people who tease you.

Show them how girly you are so as to prove that you're not a lesbian.

佢地笑你係 [lesbian]，即係話你係女同性戀者[女同志]。可能你係男仔頭打扮，或平日言行舉止太男性化。你可自我撿討有冇此傾向。
一般師姑學校都有女同志出現，不足為奇。