On the surface it looks like at best a student at Hogwarts received a 4th grade education in elementary studies before being shipped off to the famous School of Witchcraft and Wizardry and becoming forever educationally stunted. However if you look at the classes offered, you can see that they did receive at least some math, physics, reading & writing, geology, geography, chemistry, biology, and zoology, depending on electives.

First they have the option of [Muggle Studies], which is essentially an anthropology class. (http://harrypotter.wikia.com/wiki/Muggle_Studies)

This class aims specifically to acquaint wizards and witches who do not have direct contact with Muggles with the way they live; one known essay topic was "Why Muggles Need Electricity." It is an optional subject, taught from the third year to the seventh.

They also get at least 5 years of history (of magic) and astronomy.

Astronomy is one of the only fields of study at Hogwarts which has a direct equivalent in the Muggle world. Known student activities include learning the names of stars, constellations, and planets, as well as their location and movements, and describing the environments of planets and moons. - HP Wiki

Astronomy could open the door for mathematics and physics at an elementary level for the students. It could also be said that they would at least learn some geography from History of Magic.

And as mentioned in your question, Potions could be considered a form of chemistry.

Arithmancy is an elective which involved writing skills and math.

Homework assignments, which included writing essays, required the consultation and/or composition of complex number charts.

On top of that, a lot of the classes seemed to have them writing essays on subjects and the consuming of textbook material. Presumably this was the preferred form of further developing their reading and writing skills.

There is another class briefly mentioned named Earth Magic which may involve geology.

"I want to get into earth magic. I love to dig."

But overall I think it could be said that there is simply not a need for higher mathematics, biology, or anything else. Why study biology and medicine to become a doctor when you can wave your wand and say Vulnera Sanentur to heal deep gashes in a victim? Why study math and engineering when you can basically create animate objects via charms and construct virtually anything via transfiguration?

Muggles need these things because they don't have magic, but as a user of magic you don't need to, because, there is a spell for that.