Parents can opt out of state assessments such as the PSSA's and Keystone exams. Parents can also opt out of specific instruction. One of the push backs parents are getting from teachers and administrators about opting out of test prep such as CDT's and Study Island is that students are graded on these. There are a variety of ways students are assessed throughout the school year that does not include test prep.
Here is what Chapter 4 says about how students are assessed:
(c) The local assessment system shall be designed to include a variety of assessment strategies which may include the following:
(1) Written work by students.
(2) Scientific experiments conducted by students.
(3) Works of art or musical, theatrical or dance performances by students.
(4) Other demonstrations, performances, products or projects by students related to specific academic standards.
(5) Examinations developed by teachers to assess specific academic standards.
(6) Nationally-available achievement tests.
(7) Diagnostic assessments.
(8) Evaluations of portfolios of student work related to achievement of academic standards.
(9) Other measures as appropriate, which may include standardized tests.
Source: § 4.52. Local assessment system.