There are several paths you can take during the game: the PVP path, the group path, or the solo path.
If you could care less about the plot line of Wizard 101, but are interested in throwing down with other real-life people, and showing off your skill against a real person, then you like to PVP (player vs. player), and there are certain schools and spells which are better for that. (More on that in another post.)
If you have a group of friends who enjoy questing together, and doing the dungeons together, you have a lot of flexibility as to which school to choose. You will want a tank (high health, ability to taunt aggro), a healer, and a damage-dealer in your group.
But if you are solo, you need to decide which school makes it easiest to level and push through the game without help from others.
If you want to solo Wizard 101, the Ice school is for you.
Ice is characterized by mediocre damage, but high health. All of the ice-only gear has a ton of health. The damage is mediocre, but you can survive almost anything the in-game characters throw at you. Especially if you add a few life spells to your deck.
Ice as a major school, with Storm as a secondary school (the one you spend your training points in) is a pretty good combo. It gives you the survivability of Ice, with the damage of Storm.
If you want to go through Wizard 101 all by your self, try with a character that is Ice with a Storm secondary school (and a few life spells).