Mystic theurge, as you may well know considering you’re aware of Precocious Apprentice, is a massive trap. Getting 13 levels of cleric spellcasting isn’t worth 3 levels of wizard spellcasting to a wizard, and getting 13 levels of wizard spellcasting isn’t worth 3 levels of cleric spellcasting to a cleric. Combined spells is painful to actually use thanks to the spell level increase, and while spell synthesis is fantastic, it’s only once per day—not enough to warrant the costs.
My point here isn’t to dissuade you from playing a mystic theurge—both cleric and wizard have more than enough power to spare to allow a suboptimal build—but to suggest that if your GM understands the issues with mystic theurge, they might be willing to work with you here. You might be able to ask for mystic theurge to, say, advance domain features as well as cleric spellcasting, arcane school features as well as wizard spellcasting. As a GM, I would certainly allow it—I’d be worried it still wouldn’t be enough.
So the first thing you ought to do is talk to your GM about the character you want to play, the ways in which the rules are getting in the way of that character’s concept, and ask for houserules to enable your character to see the light of day. It’s my opinion that a good GM will recognize the problems with the official rules, and also be actively interested in enabling players’ characters, and therefore this will be no problem for a good GM. If your GM is mistaken about the mystic theurge’s power level, or lacks confidence for making this decision, perhaps this answer will help.
Barring that, a previous question about early entry to mystic theurge was answered (in the negative for the particular proposed approach), and those answers included some extra information—namely, a couple of ways to accomplish what you want:
Inner Sea Magic's spellcaster guilds
The Inner Sea Magic has a mechanic for being a member of a Spellcasting Guild, like an academy of magic studies, where you do some quests for them and gain fame within the academy. Then, you can obtain rewards after obtaining a certain amount of Fame, one of which is the Eclectic Training (page 22), which increases your effective caster level on a single class by +1, including spells known and able to cast.
As guild students increase in fame, they gain the
following rewards:
Eclectic Training (5 Fame): Guilds often require members to master and train in different subjects. When your Fame score in a guild reaches 5, choose one spellcasting class you have at least 1 level in—you increase your effective caster level in that class (including the number of spells you know and can cast per day) by +1, to a maximum caster level equal to your total Hit Dice. Single-classed spellcasters should still pick a class to which this bonus applies, since this bonus is retroactive.
Equipment Trick (sunrod)
Source: Pathfinder Society Field Guide
PFS Legal: Yes
Prerequisite: BAB +1
Like the Sun: You can use a sunrod as an additional material component for any spell that bears the light descriptor. The spell is treated as one spell level higher (to a maximum of 9th level) for all purposes, including the calculation of saving throw DCs and its ability to overcome sources of magical darkness.
Either of these will allow you to cast 2nd-level spells with only 2 levels in the chosen spellcasting class. The Equipment Trick actually works with just 1 level in the chosen class, since it increases a 1st-level spell to 2nd-level.
