Cheapest priced copy (Strixhaven: School of Mages): $0.35 at Card Kingdom, near mint, their price list as of .
Square Up 
Instant · Common · Strixhaven: School of Mages · #238
Target creature has base power and toughness 4/4 until end of turn.
Legal inCommanderPioneerModernLegacyVintagePauper
Not legal inBrawlStandard
1 printing · $0.35 to $0.49 at Card Kingdom
| Set | Number | Rarity | Card Kingdom | Foil |
|---|---|---|---|---|
| Strixhaven: School of Mages | 238 | Common | $0.35 | $0.49 |
2 rulings from Wizards of the Coast
- 16 April 2021Any effects that modify a creature’s power and/or toughness without setting them to a specific value (i.e. ones that don’t affect base power and/or toughness) will apply after its base power and toughness are set, regardless of the order those effects were created. The same is true for counters that modify its power and toughness.
- 16 April 2021Square Up overwrites all previous effects that set the target creature’s power and toughness to specific values. Other effects that set its power or toughness to specific values that start to apply after Square Up resolves will overwrite this effect.