We examine canonical bases for weakly holomorphic modular forms of weight 0 and level p = 2, 3, 5, 7, 13 with poles only at the cusp at ∞. We show that many of the Fourier coefficients for elements of these canonical bases are divisible by high powers of p, extending results of the first author and Andersen. Additionally, we prove similar congruences for elements of a canonical basis for the space of modular functions of level 4, and give congruences modulo arbitrary primes for coefficients of such modular functions in levels 1, 2, 3, 4, 5, 7, and 13.