Many young students have difficulty in singing pitches accurately. This will improve with practice and experience. It is important to understand the concept of different pitches, but not to worry if the student is unable to accurately reproduce them at first.
Relating pitches to the keyboard and learning the Sol-fa syllables will improve the accuracy of pitching, although some students may still take a couple of years to learn to pitch accurately.
One of the most important things about learning music is developing a good sense of time. To get you on the right track from the very beginning, it is strongly recommended that you use a metronome to play along with every time you practice.
There are various types of metronome available, from the old wind-up style metronome to the electronic metronome. Electronic metronomes are recommended because they are more accurate and often have a volume control as well as an earphone input so nobody else hears it except the person using it.