(私は)学校では遊びにくい。
(Watashi wa) gakkou de wa asobinikui.
This sentence is not incorrect. For instance, the reason is 前に先生に怒られたことがあるから "because I once was scolded by my teacher." It's the same meaning to 遊びづらい; asobizurai.
What the OP was talking about could be something like "gakkou ni wa asobiniiku
da na."
学校には遊びに行く(ん)だな as a kind of dialect...