SJSinNYC:
Halacha can be taught but ONLY actual halachos. haskafah and chumros are for the parents to teach thier children at home. (If you are afraid of your children going against a certain chumrah, such as cholov yisroel, because children often share snacks then you can make your child aware of it and tell them to be careful). (NOTE: this is NOT the place to discuss whether cholov yisroel is a chumrah or not it is just an example)
This may cause children to be influenced by kids on a diffrent haskafah level but lets be honest, kids are getting those influences anyway whether the school claims to be on a certain level or not.
This also allows for each parent to decide individually how they want thier child to be brought up rather than a principal or rebbe in a school.
As for the secular subjects i believe there should be a very strong emphasis on the secular subjects but since not everyone shares my opinion there can be diffrent tracks. Some having more learning and less secular subjects, while others have less learning but more secular subjects. (i believe such a system is used in Darchei Torah in Far Rockaway)