The GATE test is very competitive and is much harder than other school-based tests that your child has taken. The objective of the GATE test is to identify the top 2.5% of the student population. Your child should already be considered ahead of their peers at school to stand a chance. If your child is struggling or more in need of remedial help, there is little chance of success at the GATE.
However, the 4 test components in the GATE shares equal weightage; if your child is exceptionally strong in writing, this can compensate for a lower score in quantitative reasoning. The Abstract or Non-Reasoning test, in particular, can be daunting for most students who may see such questions for the first time. It is therefore good for your child to have some practice to familiarise with such questions.