I wanted to make School management software.?
You cant go wrong with Java. If you are already familiar with C++ Java will prove to be quite easy to learn. C++ and C are NOT meant for this kind of applications. Do NOT consider them. If this is going to be a web based application (and if you are not already biased against it) then PHP 7.x is also a perfectly good choice. Again, coming from C world you will be right at home with PHP.