Counterpoint: If small classes are of value to you, then small colleges will more reliably fulfill that desire.
In some large schools, the Honors College will cap class sizes. At the University of Alabama, I heard the Dean of the College of Engineering say that the Honors College classes are capped at max. 50 students, some are even smaller, like 15 students.
Some medical schools do require calculus and/or statistics. However, some schools have different versions of these courses for biology majors (pre-meds usually take the biology major version of courses, unless they are in a major that requires a different version) versus the ones for math or engineering majors. Some schools offer honors courses, which tend to be much smaller than the regular versions.
Also, many math majors are advanced in math, so they may be starting in a more advanced math course (e.g. starting in sophomore level math avoids most pre-meds, and starting in junior level math avoids most non-math majors).
CS is grown in popularity recently. Even small schools may have large introductory CS courses (e.g. around 200 at Harvey Mudd), though they can be even bigger at large schools (700-1100 or so).
Of course, there is always trying to find the balance point. If the department is very small (more common at smaller schools), then its offerings may be just at the bare minimum, with each offered every other year. If you value both small classes and a reasonably large offering of classes offered every year, you need to check the catalogs and schedules of the departments of interest at each college to see if it fulfills one or both desires.