Free, downloadable reading comprehension and sight word tests at the first grade level can be found on the Have Fun Teaching website. These tests can be used for practice or as an actual test and must be printed.
For first grade math practice, MathABC.com offers online practice. Practice tests are sorted by grade, type of math and difficulty. Eduplace.com has free online practice tests to support Houghton Mifflin Mathematics curriculum, sorted by chapter and lesson. For downloadable and printable worksheets for writing practice, Great Schools has many options that align with Common Core standards for first grade, including parts of speech and prompt writing.