We propose a method of determining the syntactic difficulty of a sentence, using syntactic patterns that identify grammatical rules on dependency parses. We have constructed a novel query language based on constraint-based dependency grammars and a grammar of German rules (relevant to primary school education) with patterns in our language. We annotated these rules with a difficulty score and grammatical prerequisites and built a matching algorithm that matches the dependency parse of a sentence in CoNLL-U format with its relevant syntactic patterns. We achieved 96% precision and 95% recall on a manually annotated set of sentences, and our best results on using parses from four parsers are 88% and 84% respectively.