1. Gainful employment is Bitual Torah, so of course the secular school curriculum is probably as well?
2. Is it mutar to speak and write languages other than Lashon Kodesh (whether mash-ups such as Yiddish, or 100% goyish languages such as English)?
3. It is permitted to make use of modern technologies (e.g antibiotics, surgery, computers, electricity, refrigeration, mechanical transportation, etc.) which can not be created or implemented without secular education? Was it permitted to use math developed by the Egyptians and Mesopotamians to calculate the calender?
4. Is it permitted to use numbers and do math (presumably beyond counting with ones fingers)? Is it permitted to engage in employment that involve interacting (as bosses, employees, customers, suppliers) with persons other than frum Yiddhe?
5. It should be noted that the rabbanim cited in the Talmuds routinely gave evidence of knowing non-Jewish languages, being familiar with the history, sociology and governance of the local goyim, doing complicated mathematical computations, and of having learned about the most advanced sciences of their day. Many of them engaged in businesses that required intimate knowledge of the goyim and their customs and sciences and culture.
So while the answer to the question is probably that while secular studies are almost by definition bitual Torah, they are permitted in a variety of conditions.