There is a set curriculum in the girls’ schools, but they still have independent say over it, and as I said, give parallel testing on that curriculum. The boys’ chadarim do what they want- some have more, some have less, some have none. The chadarim generally get less money than the BYs, AFAIK.
My memory of the details are fuzzy- so I googled it. This was a big issue for Yair Lapid et al who wanted to force the LIBA- the core curriculum on the chareidi schools- i.e. give 11 hours of secular studies/week, or else lose your funding. A law was passed, was not enforced and was repealed when the chareidim joined the government after the next round of elections, because they did not want government interference in their school system, even in those schools that did teach the minimum secular studies- an issue they are very passionate about.
This is what I found in Haaretz, from March 2017 on an article about why the Chareidi schools don’t take the standardized tests:
““We won’t allow any procedure in which the Education Ministry is involved,” Gafni said, feeling free to speak on the record. “It’s our educational independence – we decide, not the Education Ministry. We decided this back in the days of Ben-Gurion, who assured our educational independence. We won’t accept dictates, and we won’t accept the Education Ministry’s oversight.”…When it comes to funding, the Independent Education System is far from independent – the state finances it to the tune of 1.2 billion shekels ($326 million) annually.”
So yes, like so many things in E”Y, this defies logic- chareidi schools get funded (some, not all) but don’t follow the core.