A “ladder school” is supposed to elevate students from lower class backgrounds to higher classes, as Zaynab and Safia described earlier in the chapter. Saranjit, however, is (supposed to be) working just to maintain her status as a vaisya.

“Excluded” is British for “expelled.”

Side note on turbans: in 2017, at least, there are Sikh women who wear turbans, but they are a small minority. Turbans are traditionally worn by baptized men (which is, again, not all Sikh men), and women only cover their heads (if at all) with a loose scarf called a chuni. As an outsider I might have this completely wrong, but it seems to me that when a Sikh woman wears a full turban she is making a very feminist, very “all genders are the same under the law” sort of statement.

↓ Transcript
Panel 1: Davinder: "What does 'equal to your ambition' mean?"
Panel 2: Mrs. Morales-Parmar: "Ha ha." Mr. Morales-Parmar: "'Ambition' means deciding what you want and going for it."
Panel 3: Mr. Morales-Parmar: "Your sister is an excellent counter-example. Her lack of ambition has gotten her excluded from two very excellent schools."
Panel 4: Mrs. Morales-Parmar, upset: "Luis!" Saranjit, who is also upset: "Really? Are we doing this in front of the help now?" Maida tries hard to look somewhere else.
Panel 5: Mr. Morales-Parmar, getting cross: "If you can't even handle a vaisya-sudra ladder school, you will be the help, young woman! You had the potential to be a shidafu! And what have you done with it?"
Panel 6: Saranjit: "Gross! Just stop!"
Panel 7: Mrs. Morales-Parmar, as she slaps her husband on the shoulder and smiles: "Maida! How are you and Saranjit getting on togevver at school?"